enmi-conf.org: comparison wp/wp-includes/wp-db.php

equal deleted inserted replaced

-:490d5cc509ed
+:cf61fcea0001
 * file to your class. The wpdb class will still be included,
 * so you can extend it or simply use your own.
 *
 * @link https://codex.wordpress.org/Function_Reference/wpdb_Class
 *
-* @package WordPress
-* @subpackage Database
 * @since 0.71
 */
 class wpdb {
 	/**
 	 *
 	 * Default behavior is to show errors if both WP_DEBUG and WP_DEBUG_DISPLAY
 	 * evaluated to true.
 	 *
 	 * @since 0.71
-	 * @access private
 	 * @var bool
 	 */
 	var $show_errors = false;
 	/**
 	 * Whether to suppress errors during the DB bootstrapping.
 	 *
-	 * @access private
 	 * @since 2.5.0
 	 * @var bool
 	 */
 	var $suppress_errors = false;
 	/**
 	 * Amount of queries made
 	 *
 	 * @since 1.2.0
-	 * @access private
 	 * @var int
 	 */
-	var $num_queries = 0;
+	public $num_queries = 0;
 	/**
 	 * Count of rows returned by previous query
 	 *
 	 * @since 0.71
-	 * @access private
 	 * @var int
 	 */
-	var $num_rows = 0;
+	public $num_rows = 0;
 	/**
 	 * Count of affected rows by previous query
 	 *
 	 * @since 0.71
-	 * @access private
 	 * @var int
 	 */
 	var $rows_affected = 0;
 	/**
 	 * The ID generated for an AUTO_INCREMENT column by the previous query (usually INSERT).
 	 *
 	 * @since 0.71
-	 * @access public
 	 * @var int
 	 */
-	var $insert_id = 0;
+	public $insert_id = 0;
 	/**
 	 * Last query made
 	 *
 	 * @since 0.71
-	 * @access private
 	 * @var array
 	 */
 	var $last_query;
 	/**
 	 * Results of the last query made
 	 *
 	 * @since 0.71
-	 * @access private
 	 * @var array|null
 	 */
 	var $last_result;
 	/**
 	 * MySQL result, which is either a resource or boolean.
 	 *
 	 * @since 0.71
-	 * @access protected
 	 * @var mixed
 	 */
 	protected $result;
 	/**
 	 * Cached column info, for sanity checking data before inserting
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 * @var array
 	 */
 	protected $col_meta = array();
 	/**
 	 * Calculated character sets on tables
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 * @var array
 	 */
 	protected $table_charset = array();
 	/**
 	 * Whether text fields in the current query need to be sanity checked.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 * @var bool
 	 */
 	protected $check_current_query = true;
 	/**
 	 * Flag to ensure we don't run into recursion problems when checking the collation.
 	 *
 	 * @since 4.2.0
-	 * @access private
 	 * @see wpdb::check_safe_collation()
-	 * @var boolean
+	 * @var bool
 	 */
 	private $checking_collation = false;
 	/**
 	 * Saved info on the table column
 	 *
 	 * @since 0.71
-	 * @access protected
 	 * @var array
 	 */
 	protected $col_info;
 	/**
 	 * Saved queries that were executed
 	 *
 	 * @since 1.5.0
-	 * @access private
 	 * @var array
 	 */
 	var $queries;
 	/**
 	 * The number of times to retry reconnecting before dying.
 	 *
 	 * @since 3.9.0
-	 * @access protected
 	 * @see wpdb::check_connection()
 	 * @var int
 	 */
 	protected $reconnect_retries = 5;
 	 * You can set this to have multiple WordPress installations
 	 * in a single database. The second reason is for possible
 	 * security precautions.
 	 *
 	 * @since 2.5.0
-	 * @access private
 	 * @var string
 	 */
-	var $prefix = '';
+	public $prefix = '';
 	/**
 	 * WordPress base table prefix.
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	 public $base_prefix;
 	/**
 	 * Whether the database queries are ready to start executing.
 	 *
 	 * @since 2.3.2
-	 * @access private
 	 * @var bool
 	 */
 	var $ready = false;
 	/**
 	 * Blog ID.
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var int
 	 */
 	public $blogid = 0;
 	/**
 	 * Site ID.
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var int
 	 */
 	public $siteid = 0;
 	/**
 	 * List of WordPress per-blog tables
 	 *
 	 * @since 2.5.0
-	 * @access private
 	 * @see wpdb::tables()
 	 * @var array
 	 */
 	var $tables = array( 'posts', 'comments', 'links', 'options', 'postmeta',
-		'terms', 'term_taxonomy', 'term_relationships', 'commentmeta' );
+		'terms', 'term_taxonomy', 'term_relationships', 'termmeta', 'commentmeta' );
 	/**
 	 * List of deprecated WordPress tables
 	 *
 	 * categories, post2cat, and link2cat were deprecated in 2.3.0, db version 5539
 	 *
 	 * @since 2.9.0
-	 * @access private
 	 * @see wpdb::tables()
 	 * @var array
 	 */
 	var $old_tables = array( 'categories', 'post2cat', 'link2cat' );
 	/**
 	 * List of WordPress global tables
 	 *
 	 * @since 3.0.0
-	 * @access private
 	 * @see wpdb::tables()
 	 * @var array
 	 */
 	var $global_tables = array( 'users', 'usermeta' );
 	/**
 	 * List of Multisite global tables
 	 *
 	 * @since 3.0.0
-	 * @access private
 	 * @see wpdb::tables()
 	 * @var array
 	 */
 	var $ms_global_tables = array( 'blogs', 'signups', 'site', 'sitemeta',
 		'sitecategories', 'registration_log', 'blog_versions' );
 	/**
 	 * WordPress Comments table
 	 *
 	 * @since 1.5.0
-	 * @access public
 	 * @var string
 	 */
 	public $comments;
 	/**
 	 * WordPress Comment Metadata table
 	 *
 	 * @since 2.9.0
-	 * @access public
 	 * @var string
 	 */
 	public $commentmeta;
 	/**
 	 * WordPress Links table
 	 *
 	 * @since 1.5.0
-	 * @access public
 	 * @var string
 	 */
 	public $links;
 	/**
 	 * WordPress Options table
 	 *
 	 * @since 1.5.0
-	 * @access public
 	 * @var string
 	 */
 	public $options;
 	/**
 	 * WordPress Post Metadata table
 	 *
 	 * @since 1.5.0
-	 * @access public
 	 * @var string
 	 */
 	public $postmeta;
 	/**
 	 * WordPress Posts table
 	 *
 	 * @since 1.5.0
-	 * @access public
 	 * @var string
 	 */
 	public $posts;
 	/**
 	 * WordPress Terms table
 	 *
 	 * @since 2.3.0
-	 * @access public
 	 * @var string
 	 */
 	public $terms;
 	/**
 	 * WordPress Term Relationships table
 	 *
 	 * @since 2.3.0
-	 * @access public
 	 * @var string
 	 */
 	public $term_relationships;
 	/**
 	 * WordPress Term Taxonomy table
 	 *
 	 * @since 2.3.0
-	 * @access public
 	 * @var string
 	 */
 	public $term_taxonomy;
-	/*
+	/**
-	 * Global and Multisite tables
+	 * WordPress Term Meta table.
-	 */
+	 *
+	 * @since 4.4.0
+	 * @var string
+	 */
+	public $termmeta;
+	//
+	// Global and Multisite tables
+	//
 	/**
 	 * WordPress User Metadata table
 	 *
 	 * @since 2.3.0
-	 * @access public
 	 * @var string
 	 */
 	public $usermeta;
 	/**
 	 * WordPress Users table
 	 *
 	 * @since 1.5.0
-	 * @access public
 	 * @var string
 	 */
 	public $users;
 	/**
 	 * Multisite Blogs table
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $blogs;
 	/**
 	 * Multisite Blog Versions table
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $blog_versions;
 	/**
 	 * Multisite Registration Log table
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $registration_log;
 	/**
 	 * Multisite Signups table
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $signups;
 	/**
 	 * Multisite Sites table
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $site;
 	/**
 	 * Multisite Sitewide Terms table
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $sitecategories;
 	/**
 	 * Multisite Site Metadata table
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $sitemeta;
 	/**
 	 * @see wpdb::prepare()
 	 * @see wpdb::insert()
 	 * @see wpdb::update()
 	 * @see wpdb::delete()
 	 * @see wp_set_wpdb_vars()
-	 * @access public
 	 * @var array
 	 */
 	public $field_types = array();
 	/**
 	 * Database table columns charset
 	 *
 	 * @since 2.2.0
-	 * @access public
 	 * @var string
 	 */
 	public $charset;
 	/**
 	 * Database table columns collate
 	 *
 	 * @since 2.2.0
-	 * @access public
 	 * @var string
 	 */
 	public $collate;
 	/**
 	 * Database Username
 	 *
 	 * @since 2.9.0
-	 * @access protected
 	 * @var string
 	 */
 	protected $dbuser;
 	/**
 	 * Database Password
 	 *
 	 * @since 3.1.0
-	 * @access protected
 	 * @var string
 	 */
 	protected $dbpassword;
 	/**
 	 * Database Name
 	 *
 	 * @since 3.1.0
-	 * @access protected
 	 * @var string
 	 */
 	protected $dbname;
 	/**
 	 * Database Host
 	 *
 	 * @since 3.1.0
-	 * @access protected
 	 * @var string
 	 */
 	protected $dbhost;
 	/**
 	 * Database Handle
 	 *
 	 * @since 0.71
-	 * @access protected
 	 * @var string
 	 */
 	protected $dbh;
 	/**
 	 * A textual description of the last query/get_row/get_var call
 	 *
 	 * @since 3.0.0
-	 * @access public
 	 * @var string
 	 */
 	public $func_call;
 	/**
 	 * against the required MySQL version for WordPress. Normally, a replacement
 	 * database drop-in (db.php) will skip these checks, but setting this to true
 	 * will force the checks to occur.
 	 *
 	 * @since 3.3.0
-	 * @access public
 	 * @var bool
 	 */
 	public $is_mysql = null;
 	/**
 	 * A list of incompatible SQL modes.
 	 *
 	 * @since 3.9.0
-	 * @access protected
 	 * @var array
 	 */
 	protected $incompatible_modes = array( 'NO_ZERO_DATE', 'ONLY_FULL_GROUP_BY',
 		'STRICT_TRANS_TABLES', 'STRICT_ALL_TABLES', 'TRADITIONAL' );
 	/**
 	 * Whether to use mysqli over mysql.
 	 *
 	 * @since 3.9.0
-	 * @access private
 	 * @var bool
 	 */
 	private $use_mysqli = false;
 	/**
 	 * Whether we've managed to successfully connect at some point
 	 *
 	 * @since 3.9.0
-	 * @access private
 	 * @var bool
 	 */
 	private $has_connected = false;
 	/**
 	 * to the database.
 	 *
 	 * @link https://core.trac.wordpress.org/ticket/3354
 	 * @since 2.0.8
 	 *
-	 * @param string $dbuser MySQL database user
+	 * @global string $wp_version
+	 *
+	 * @param string $dbuser     MySQL database user
 	 * @param string $dbpassword MySQL database password
-	 * @param string $dbname MySQL database name
+	 * @param string $dbname     MySQL database name
-	 * @param string $dbhost MySQL database host
+	 * @param string $dbhost     MySQL database host
 	 */
 	public function __construct( $dbuser, $dbpassword, $dbname, $dbhost ) {
 		register_shutdown_function( array( $this, '__destruct' ) );
 		if ( WP_DEBUG && WP_DEBUG_DISPLAY )
 			$this->show_errors();
-		/* Use ext/mysqli if it exists and:
+		// Use ext/mysqli if it exists unless WP_USE_EXT_MYSQL is defined as true
-		 *  - WP_USE_EXT_MYSQL is defined as false, or
-		 *  - We are a development version of WordPress, or
-		 *  - We are running PHP 5.5 or greater, or
-		 *  - ext/mysql is not loaded.
-		 */
 		if ( function_exists( 'mysqli_connect' ) ) {
+			$this->use_mysqli = true;
 			if ( defined( 'WP_USE_EXT_MYSQL' ) ) {
 				$this->use_mysqli = ! WP_USE_EXT_MYSQL;
-			} elseif ( version_compare( phpversion(), '5.5', '>=' ) || ! function_exists( 'mysql_connect' ) ) {
-				$this->use_mysqli = true;
-			} elseif ( false !== strpos( $GLOBALS['wp_version'], '-' ) ) {
-				$this->use_mysqli = true;
 			}
 		}
 		$this->dbuser = $dbuser;
 		$this->dbpassword = $dbpassword;
 	/**
 	 * PHP5 style destructor and will run when database object is destroyed.
 	 *
 	 * @see wpdb::__construct()
 	 * @since 2.0.8
-	 * @return bool true
+	 * @return true
 	 */
 	public function __destruct() {
 		return true;
 	}
 	/**
-	 * PHP5 style magic getter, used to lazy-load expensive data.
+	 * Makes private properties readable for backward compatibility.
 	 *
 	 * @since 3.5.0
 	 *
 	 * @param string $name The private member to get, and optionally process
 	 * @return mixed The private member
 		return $this->$name;
 	}
 	/**
-	 * Magic function, for backwards compatibility.
+	 * Makes private properties settable for backward compatibility.
 	 *
 	 * @since 3.5.0
 	 *
 	 * @param string $name  The private member to set
 	 * @param mixed  $value The value to set
 		}
 		$this->$name = $value;
 	}
 	/**
-	 * Magic function, for backwards compatibility.
+	 * Makes private properties check-able for backward compatibility.
 	 *
 	 * @since 3.5.0
 	 *
 	 * @param string $name  The private member to check
 	 *
 	public function __isset( $name ) {
 		return isset( $this->$name );
 	}
 	/**
-	 * Magic function, for backwards compatibility.
+	 * Makes private properties un-settable for backward compatibility.
 	 *
 	 * @since 3.5.0
 	 *
 	 * @param string $name  The private member to unset
 	 */
 	 * Set $this->charset and $this->collate
 	 *
 	 * @since 3.1.0
 	 */
 	public function init_charset() {
+		$charset = '';
+		$collate = '';
 		if ( function_exists('is_multisite') && is_multisite() ) {
-			$this->charset = 'utf8';
+			$charset = 'utf8';
 			if ( defined( 'DB_COLLATE' ) && DB_COLLATE ) {
-				$this->collate = DB_COLLATE;
+				$collate = DB_COLLATE;
 			} else {
-				$this->collate = 'utf8_general_ci';
+				$collate = 'utf8_general_ci';
 			}
 		} elseif ( defined( 'DB_COLLATE' ) ) {
-			$this->collate = DB_COLLATE;
+			$collate = DB_COLLATE;
 		}
 		if ( defined( 'DB_CHARSET' ) ) {
-			$this->charset = DB_CHARSET;
+			$charset = DB_CHARSET;
 		}
-		if ( ( $this->use_mysqli && ! ( $this->dbh instanceof mysqli ) )
+		$charset_collate = $this->determine_charset( $charset, $collate );
-		  || ( empty( $this->dbh ) || ! ( $this->dbh instanceof mysqli ) ) ) {
-			return;
+		$this->charset = $charset_collate['charset'];
-		}
+		$this->collate = $charset_collate['collate'];
+	}
-		if ( 'utf8' === $this->charset && $this->has_cap( 'utf8mb4' ) ) {
-			$this->charset = 'utf8mb4';
+	/**
-		}
+	 * Determines the best charset and collation to use given a charset and collation.
+	 *
-		if ( 'utf8mb4' === $this->charset && ( ! $this->collate || stripos( $this->collate, 'utf8_' ) === 0 ) ) {
+	 * For example, when able, utf8mb4 should be used instead of utf8.
-			$this->collate = 'utf8mb4_unicode_ci';
+	 *
-		}
+	 * @since 4.6.0
+	 *
+	 * @param string $charset The character set to check.
+	 * @param string $collate The collation to check.
+	 * @return array The most appropriate character set and collation to use.
+	 */
+	public function determine_charset( $charset, $collate ) {
+		if ( ( $this->use_mysqli && ! ( $this->dbh instanceof mysqli ) ) || empty( $this->dbh ) ) {
+			return compact( 'charset', 'collate' );
+		}
+		if ( 'utf8' === $charset && $this->has_cap( 'utf8mb4' ) ) {
+			$charset = 'utf8mb4';
+		}
+		if ( 'utf8mb4' === $charset && ! $this->has_cap( 'utf8mb4' ) ) {
+			$charset = 'utf8';
+			$collate = str_replace( 'utf8mb4_', 'utf8_', $collate );
+		}
+		if ( 'utf8mb4' === $charset ) {
+			// _general_ is outdated, so we can upgrade it to _unicode_, instead.
+			if ( ! $collate || 'utf8_general_ci' === $collate ) {
+				$collate = 'utf8mb4_unicode_ci';
+			} else {
+				$collate = str_replace( 'utf8_', 'utf8mb4_', $collate );
+			}
+		}
+		// _unicode_520_ is a better collation, we should use that when it's available.
+		if ( $this->has_cap( 'utf8mb4_520' ) && 'utf8mb4_unicode_ci' === $collate ) {
+			$collate = 'utf8mb4_unicode_520_ci';
+		}
+		return compact( 'charset', 'collate' );
 	}
 	/**
 	 * Sets the connection's character set.
 	 *
 		if ( ! isset( $charset ) )
 			$charset = $this->charset;
 		if ( ! isset( $collate ) )
 			$collate = $this->collate;
 		if ( $this->has_cap( 'collation' ) && ! empty( $charset ) ) {
+			$set_charset_succeeded = true;
 			if ( $this->use_mysqli ) {
 				if ( function_exists( 'mysqli_set_charset' ) && $this->has_cap( 'set_charset' ) ) {
-					mysqli_set_charset( $dbh, $charset );
+					$set_charset_succeeded = mysqli_set_charset( $dbh, $charset );
-				} else {
+				}
+				if ( $set_charset_succeeded ) {
 					$query = $this->prepare( 'SET NAMES %s', $charset );
 					if ( ! empty( $collate ) )
 						$query .= $this->prepare( ' COLLATE %s', $collate );
 					mysqli_query( $dbh, $query );
 				}
 			} else {
 				if ( function_exists( 'mysql_set_charset' ) && $this->has_cap( 'set_charset' ) ) {
-					mysql_set_charset( $charset, $dbh );
+					$set_charset_succeeded = mysql_set_charset( $charset, $dbh );
-				} else {
+				}
+				if ( $set_charset_succeeded ) {
 					$query = $this->prepare( 'SET NAMES %s', $charset );
 					if ( ! empty( $collate ) )
 						$query .= $this->prepare( ' COLLATE %s', $collate );
 					mysql_query( $query, $dbh );
 				}
 		}
 		$modes = array_change_key_case( $modes, CASE_UPPER );
 		/**
-		 * Filter the list of incompatible SQL modes to exclude.
+		 * Filters the list of incompatible SQL modes to exclude.
 		 *
 		 * @since 3.9.0
 		 *
 		 * @param array $incompatible_modes An array of incompatible modes.
 		 */
 		$incompatible_modes = (array) apply_filters( 'incompatible_sql_modes', $this->incompatible_modes );
-		foreach( $modes as $i => $mode ) {
+		foreach ( $modes as $i => $mode ) {
 			if ( in_array( $mode, $incompatible_modes ) ) {
 				unset( $modes[ $i ] );
 			}
 		}
 	/**
 	 * Sets the table prefix for the WordPress tables.
 	 *
 	 * @since 2.5.0
 	 *
-	 * @param string $prefix Alphanumeric name for the new prefix.
+	 * @param string $prefix          Alphanumeric name for the new prefix.
-	 * @param bool $set_table_names Optional. Whether the table names, e.g. wpdb::$posts, should be updated or not.
+	 * @param bool   $set_table_names Optional. Whether the table names, e.g. wpdb::$posts, should be updated or not.
 	 * @return string|WP_Error Old prefix or WP_Error on error
 	 */
 	public function set_prefix( $prefix, $set_table_names = true ) {
 		if ( preg_match( '|[^a-z0-9_]|i', $prefix ) )
 	/**
 	 * Sets blog id.
 	 *
 	 * @since 3.0.0
-	 * @access public
+	 *
 	 * @param int $blog_id
-	 * @param int $site_id Optional.
+	 * @param int $network_id Optional.
 	 * @return int previous blog id
 	 */
-	public function set_blog_id( $blog_id, $site_id = 0 ) {
+	public function set_blog_id( $blog_id, $network_id = 0 ) {
-		if ( ! empty( $site_id ) )
+		if ( ! empty( $network_id ) ) {
-			$this->siteid = $site_id;
+			$this->siteid = $network_id;
+		}
 		$old_blog_id  = $this->blogid;
 		$this->blogid = $blog_id;
 		$this->prefix = $this->get_blog_prefix();
 	 * @uses wpdb::$tables
 	 * @uses wpdb::$old_tables
 	 * @uses wpdb::$global_tables
 	 * @uses wpdb::$ms_global_tables
 	 *
-	 * @param string $scope Optional. Can be all, global, ms_global, blog, or old tables. Defaults to all.
+	 * @param string $scope   Optional. Can be all, global, ms_global, blog, or old tables. Defaults to all.
-	 * @param bool $prefix Optional. Whether to include table prefixes. Default true. If blog
+	 * @param bool   $prefix  Optional. Whether to include table prefixes. Default true. If blog
-	 * 	prefix is requested, then the custom users and usermeta tables will be mapped.
+	 *                        prefix is requested, then the custom users and usermeta tables will be mapped.
-	 * @param int $blog_id Optional. The blog_id to prefix. Defaults to wpdb::$blogid. Used only when prefix is requested.
+	 * @param int    $blog_id Optional. The blog_id to prefix. Defaults to wpdb::$blogid. Used only when prefix is requested.
 	 * @return array Table names. When a prefix is requested, the key is the unprefixed table name.
 	 */
 	public function tables( $scope = 'all', $prefix = true, $blog_id = 0 ) {
 		switch ( $scope ) {
 			case 'all' :
 	 * The database name will be changed based on the current database
 	 * connection. On failure, the execution will bail and display an DB error.
 	 *
 	 * @since 0.71
 	 *
-	 * @param string $db MySQL database name
+	 * @param string        $db  MySQL database name
-	 * @param resource $dbh Optional link identifier.
+	 * @param resource|null $dbh Optional link identifier.
-	 * @return null Always null.
 	 */
 	public function select( $db, $dbh = null ) {
 		if ( is_null($dbh) )
 			$dbh = $this->dbh;
 		if ( $this->use_mysqli ) {
-			$success = @mysqli_select_db( $dbh, $db );
+			$success = mysqli_select_db( $dbh, $db );
 		} else {
-			$success = @mysql_select_db( $db, $dbh );
+			$success = mysql_select_db( $db, $dbh );
 		}
 		if ( ! $success ) {
 			$this->ready = false;
 			if ( ! did_action( 'template_redirect' ) ) {
 				wp_load_translations_early();
-				$this->bail( sprintf( __( '<h1>Can&#8217;t select database</h1>
-<p>We were able to connect to the database server (which means your username and password is okay) but not able to select the <code>%1$s</code> database.</p>
+				$message = '<h1>' . __( 'Can&#8217;t select database' ) . "</h1>\n";
-<ul>
-<li>Are you sure it exists?</li>
+				$message .= '<p>' . sprintf(
-<li>Does the user <code>%2$s</code> have permission to use the <code>%1$s</code> database?</li>
+					/* translators: %s: database name */
-<li>On some systems the name of your database is prefixed with your username, so it would be like <code>username_%1$s</code>. Could that be the problem?</li>
+					__( 'We were able to connect to the database server (which means your username and password is okay) but not able to select the %s database.' ),
-</ul>
+					'<code>' . htmlspecialchars( $db, ENT_QUOTES ) . '</code>'
-<p>If you don\'t know how to set up a database you should <strong>contact your host</strong>. If all else fails you may find help at the <a href="https://wordpress.org/support/">WordPress Support Forums</a>.</p>' ), htmlspecialchars( $db, ENT_QUOTES ), htmlspecialchars( $this->dbuser, ENT_QUOTES ) ), 'db_select_fail' );
+				) . "</p>\n";
-			}
-			return;
+				$message .= "<ul>\n";
+				$message .= '<li>' . __( 'Are you sure it exists?' ) . "</li>\n";
+				$message .= '<li>' . sprintf(
+					/* translators: 1: database user, 2: database name */
+					__( 'Does the user %1$s have permission to use the %2$s database?' ),
+					'<code>' . htmlspecialchars( $this->dbuser, ENT_QUOTES )  . '</code>',
+					'<code>' . htmlspecialchars( $db, ENT_QUOTES ) . '</code>'
+				) . "</li>\n";
+				$message .= '<li>' . sprintf(
+					/* translators: %s: database name */
+					__( 'On some systems the name of your database is prefixed with your username, so it would be like <code>username_%1$s</code>. Could that be the problem?' ),
+					htmlspecialchars( $db, ENT_QUOTES )
+				). "</li>\n";
+				$message .= "</ul>\n";
+				$message .= '<p>' . sprintf(
+					/* translators: %s: support forums URL */
+					__( 'If you don&#8217;t know how to set up a database you should <strong>contact your host</strong>. If all else fails you may find help at the <a href="%s">WordPress Support Forums</a>.' ),
+					__( 'https://wordpress.org/support/' )
+				) . "</p>\n";
+				$this->bail( $message, 'db_select_fail' );
+			}
 		}
 	}
 	/**
 	 * Do not use, deprecated.
 	 *
 	 * Use esc_sql() or wpdb::prepare() instead.
 	 *
 	 * @since 2.8.0
-	 * @deprecated 3.6.0
+	 * @deprecated 3.6.0 Use wpdb::prepare()
 	 * @see wpdb::prepare
 	 * @see esc_sql()
-	 * @access private
 	 *
 	 * @param string $string
 	 * @return string
 	 */
 	function _weak_escape( $string ) {
 		if ( func_num_args() === 1 && function_exists( '_deprecated_function' ) )
-			_deprecated_function( __METHOD__, '3.6', 'wpdb::prepare() or esc_sql()' );
+			_deprecated_function( __METHOD__, '3.6.0', 'wpdb::prepare() or esc_sql()' );
 		return addslashes( $string );
 	}
 	/**
 	 * Real escape, using mysqli_real_escape_string() or mysql_real_escape_string()
 	 *
 	 * @see mysqli_real_escape_string()
 	 * @see mysql_real_escape_string()
 	 * @since 2.8.0
-	 * @access private
 	 *
 	 * @param  string $string to escape
 	 * @return string escaped
 	 */
 	function _real_escape( $string ) {
 		if ( $this->dbh ) {
 			if ( $this->use_mysqli ) {
-				return mysqli_real_escape_string( $this->dbh, $string );
+				$escaped = mysqli_real_escape_string( $this->dbh, $string );
 			} else {
-				return mysql_real_escape_string( $string, $this->dbh );
+				$escaped = mysql_real_escape_string( $string, $this->dbh );
 			}
-		}
-		$class = get_class( $this );
-		if ( function_exists( '__' ) ) {
-			_doing_it_wrong( $class, sprintf( __( '%s must set a database connection for use with escaping.' ), $class ), E_USER_NOTICE );
 		} else {
-			_doing_it_wrong( $class, sprintf( '%s must set a database connection for use with escaping.', $class ), E_USER_NOTICE );
+			$class = get_class( $this );
-		}
+			if ( function_exists( '__' ) ) {
-		return addslashes( $string );
+				/* translators: %s: database access abstraction class, usually wpdb or a class extending wpdb */
+				_doing_it_wrong( $class, sprintf( __( '%s must set a database connection for use with escaping.' ), $class ), '3.6.0' );
+			} else {
+				_doing_it_wrong( $class, sprintf( '%s must set a database connection for use with escaping.', $class ), '3.6.0' );
+			}
+			$escaped = addslashes( $string );
+		}
+		return $this->add_placeholder_escape( $escaped );
 	}
 	/**
 	 * Escape data. Works on arrays.
 	 *
 	 * @uses wpdb::_real_escape()
 	 * @since  2.8.0
-	 * @access private
 	 *
 	 * @param  string|array $data
 	 * @return string|array escaped
 	 */
-	function _escape( $data ) {
+	public function _escape( $data ) {
 		if ( is_array( $data ) ) {
 			foreach ( $data as $k => $v ) {
-				if ( is_array($v) )
+				if ( is_array( $v ) ) {
 					$data[$k] = $this->_escape( $v );
-				else
+				} else {
 					$data[$k] = $this->_real_escape( $v );
+				}
 			}
 		} else {
 			$data = $this->_real_escape( $data );
 		}
 	 * Do not use, deprecated.
 	 *
 	 * Use esc_sql() or wpdb::prepare() instead.
 	 *
 	 * @since 0.71
-	 * @deprecated 3.6.0
+	 * @deprecated 3.6.0 Use wpdb::prepare()
 	 * @see wpdb::prepare()
 	 * @see esc_sql()
 	 *
 	 * @param mixed $data
 	 * @return mixed
 	 */
 	public function escape( $data ) {
 		if ( func_num_args() === 1 && function_exists( '_deprecated_function' ) )
-			_deprecated_function( __METHOD__, '3.6', 'wpdb::prepare() or esc_sql()' );
+			_deprecated_function( __METHOD__, '3.6.0', 'wpdb::prepare() or esc_sql()' );
 		if ( is_array( $data ) ) {
 			foreach ( $data as $k => $v ) {
 				if ( is_array( $v ) )
 					$data[$k] = $this->escape( $v, 'recursive' );
 				else
 	/**
 	 * Escapes content by reference for insertion into the database, for security
 	 *
 	 * @uses wpdb::_real_escape()
+	 *
 	 * @since 2.3.0
+	 *
 	 * @param string $string to escape
-	 * @return void
 	 */
 	public function escape_by_ref( &$string ) {
 		if ( ! is_float( $string ) )
 			$string = $this->_real_escape( $string );
 	}
 	/**
 	 * Prepares a SQL query for safe execution. Uses sprintf()-like syntax.
 	 *
-	 * The following directives can be used in the query format string:
+	 * The following placeholders can be used in the query string:
 	 *   %d (integer)
 	 *   %f (float)
 	 *   %s (string)
-	 *   %% (literal percentage sign - no argument needed)
+	 *
-	 *
+	 * All placeholders MUST be left unquoted in the query string. A corresponding argument MUST be passed for each placeholder.
-	 * All of %d, %f, and %s are to be left unquoted in the query string and they need an argument passed for them.
+	 *
-	 * Literals (%) as parts of the query must be properly written as %%.
+	 * For compatibility with old behavior, numbered or formatted string placeholders (eg, %1$s, %5s) will not have quotes
-	 *
+	 * added by this function, so should be passed with appropriate quotes around them for your usage.
-	 * This function only supports a small subset of the sprintf syntax; it only supports %d (integer), %f (float), and %s (string).
+	 *
-	 * Does not support sign, padding, alignment, width or precision specifiers.
+	 * Literal percentage signs (%) in the query string must be written as %%. Percentage wildcards (for example,
-	 * Does not support argument numbering/swapping.
+	 * to use in LIKE syntax) must be passed via a substitution argument containing the complete LIKE string, these
-	 *
+	 * cannot be inserted directly in the query string. Also see {@see esc_like()}.
-	 * May be called like {@link http://php.net/sprintf sprintf()} or like {@link http://php.net/vsprintf vsprintf()}.
+	 *
-	 *
+	 * Arguments may be passed as individual arguments to the method, or as a single array containing all arguments. A combination
-	 * Both %d and %s should be left unquoted in the query string.
+	 * of the two is not supported.
 	 *
-	 *     wpdb::prepare( "SELECT * FROM `table` WHERE `column` = %s AND `field` = %d", 'foo', 1337 )
+	 * Examples:
-	 *     wpdb::prepare( "SELECT DATE_FORMAT(`field`, '%%c') FROM `table` WHERE `column` = %s", 'foo' );
+	 *     $wpdb->prepare( "SELECT * FROM `table` WHERE `column` = %s AND `field` = %d OR `other_field` LIKE %s", array( 'foo', 1337, '%bar' ) );
-	 *
+	 *     $wpdb->prepare( "SELECT DATE_FORMAT(`field`, '%%c') FROM `table` WHERE `column` = %s", 'foo' );
-	 * @link http://php.net/sprintf Description of syntax.
+	 *
+	 * @link https://secure.php.net/sprintf Description of syntax.
 	 * @since 2.3.0
 	 *
-	 * @param string $query Query statement with sprintf()-like placeholders
+	 * @param string      $query    Query statement with sprintf()-like placeholders
-	 * @param array|mixed $args The array of variables to substitute into the query's placeholders if being called like
+	 * @param array|mixed $args     The array of variables to substitute into the query's placeholders if being called with an array of arguments,
-	 * 	{@link http://php.net/vsprintf vsprintf()}, or the first variable to substitute into the query's placeholders if
+	 *                              or the first variable to substitute into the query's placeholders if being called with individual arguments.
-	 * 	being called like {@link http://php.net/sprintf sprintf()}.
+	 * @param mixed       $args,... further variables to substitute into the query's placeholders if being called wih individual arguments.
-	 * @param mixed $args,... further variables to substitute into the query's placeholders if being called like
+	 * @return string|void Sanitized query string, if there is a query to prepare.
-	 * 	{@link http://php.net/sprintf sprintf()}.
-	 * @return null|false|string Sanitized query string, null if there is no query, false if there is an error and string
-	 * 	if there was something to prepare
 	 */
 	public function prepare( $query, $args ) {
-		if ( is_null( $query ) )
+		if ( is_null( $query ) ) {
 			return;
+		}
 		// This is not meant to be foolproof -- but it will catch obviously incorrect usage.
 		if ( strpos( $query, '%' ) === false ) {
-			_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'The query argument of %s must have a placeholder.' ), 'wpdb::prepare()' ), '3.9' );
+			wp_load_translations_early();
+			_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'The query argument of %s must have a placeholder.' ), 'wpdb::prepare()' ), '3.9.0' );
 		}
 		$args = func_get_args();
 		array_shift( $args );
-		// If args were passed as an array (as in vsprintf), move them up
-		if ( isset( $args[0] ) && is_array($args[0]) )
+		// If args were passed as an array (as in vsprintf), move them up.
+		$passed_as_array = false;
+		if ( is_array( $args[0] ) && count( $args ) == 1 ) {
+			$passed_as_array = true;
 			$args = $args[0];
-		$query = str_replace( "'%s'", '%s', $query ); // in case someone mistakenly already singlequoted it
+		}
-		$query = str_replace( '"%s"', '%s', $query ); // doublequote unquoting
-		$query = preg_replace( '|(?<!%)%f|' , '%F', $query ); // Force floats to be locale unaware
+		foreach ( $args as $arg ) {
-		$query = preg_replace( '|(?<!%)%s|', "'%s'", $query ); // quote the strings, avoiding escaped strings like %%s
+			if ( ! is_scalar( $arg ) && ! is_null( $arg ) ) {
+				wp_load_translations_early();
+				_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'Unsupported value type (%s).' ), gettype( $arg ) ), '4.8.2' );
+			}
+		}
+		/*
+		 * Specify the formatting allowed in a placeholder. The following are allowed:
+		 *
+		 * - Sign specifier. eg, $+d
+		 * - Numbered placeholders. eg, %1$s
+		 * - Padding specifier, including custom padding characters. eg, %05s, %'#5s
+		 * - Alignment specifier. eg, %05-s
+		 * - Precision specifier. eg, %.2f
+		 */
+		$allowed_format = '(?:[1-9][0-9]*[$])?[-+0-9]*(?: |0|\'.)?[-+0-9]*(?:\.[0-9]+)?';
+		/*
+		 * If a %s placeholder already has quotes around it, removing the existing quotes and re-inserting them
+		 * ensures the quotes are consistent.
+		 *
+		 * For backwards compatibility, this is only applied to %s, and not to placeholders like %1$s, which are frequently
+		 * used in the middle of longer strings, or as table name placeholders.
+		 */
+		$query = str_replace( "'%s'", '%s', $query ); // Strip any existing single quotes.
+		$query = str_replace( '"%s"', '%s', $query ); // Strip any existing double quotes.
+		$query = preg_replace( '/(?<!%)%s/', "'%s'", $query ); // Quote the strings, avoiding escaped strings like %%s.
+		$query = preg_replace( "/(?<!%)(%($allowed_format)?f)/" , '%\\2F', $query ); // Force floats to be locale unaware.
+		$query = preg_replace( "/%(?:%|$|(?!($allowed_format)?[sdF]))/", '%%\\1', $query ); // Escape any unescaped percents.
+		// Count the number of valid placeholders in the query.
+		$placeholders = preg_match_all( "/(^|[^%]|(%%)+)%($allowed_format)?[sdF]/", $query, $matches );
+		if ( count( $args ) !== $placeholders ) {
+			if ( 1 === $placeholders && $passed_as_array ) {
+				// If the passed query only expected one argument, but the wrong number of arguments were sent as an array, bail.
+				wp_load_translations_early();
+				_doing_it_wrong( 'wpdb::prepare', __( 'The query only expected one placeholder, but an array of multiple placeholders was sent.' ), '4.9.0' );
+				return;
+			} else {
+				/*
+				 * If we don't have the right number of placeholders, but they were passed as individual arguments,
+				 * or we were expecting multiple arguments in an array, throw a warning.
+				 */
+				wp_load_translations_early();
+				_doing_it_wrong( 'wpdb::prepare',
+					/* translators: 1: number of placeholders, 2: number of arguments passed */
+					sprintf( __( 'The query does not contain the correct number of placeholders (%1$d) for the number of arguments passed (%2$d).' ),
+						$placeholders,
+						count( $args ) ),
+					'4.8.3'
+				);
+			}
+		}
 		array_walk( $args, array( $this, 'escape_by_ref' ) );
-		return @vsprintf( $query, $args );
+		$query = @vsprintf( $query, $args );
+		return $this->add_placeholder_escape( $query );
 	}
 	/**
 	 * First half of escaping for LIKE special characters % and _ before preparing for MySQL.
 	 *
 	 * Use this only before wpdb::prepare() or esc_sql().  Reversing the order is very bad for security.
 	 *
 	 * Example Prepared Statement:
-	 *  $wild = '%';
+	 *
-	 *  $find = 'only 43% of planets';
+	 *     $wild = '%';
-	 *  $like = $wild . $wpdb->esc_like( $find ) . $wild;
+	 *     $find = 'only 43% of planets';
-	 *  $sql  = $wpdb->prepare( "SELECT * FROM $wpdb->posts WHERE post_content LIKE %s", $like );
+	 *     $like = $wild . $wpdb->esc_like( $find ) . $wild;
+	 *     $sql  = $wpdb->prepare( "SELECT * FROM $wpdb->posts WHERE post_content LIKE %s", $like );
 	 *
 	 * Example Escape Chain:
-	 *  $sql  = esc_sql( $wpdb->esc_like( $input ) );
+	 *
+	 *     $sql  = esc_sql( $wpdb->esc_like( $input ) );
 	 *
 	 * @since 4.0.0
-	 * @access public
 	 *
 	 * @param string $text The raw text to be escaped. The input typed by the user should have no
 	 *                     extra or deleted slashes.
 	 * @return string Text in the form of a LIKE phrase. The output is not SQL safe. Call $wpdb::prepare()
 	 *                or real_escape next.
 	 *
 	 * @since 0.71
 	 * @global array $EZSQL_ERROR Stores error information of query and error string
 	 *
 	 * @param string $str The error to display
-	 * @return false|null False if the showing of errors is disabled.
+	 * @return false|void False if the showing of errors is disabled.
 	 */
 	public function print_error( $str = '' ) {
 		global $EZSQL_ERROR;
 		if ( !$str ) {
 		if ( $this->suppress_errors )
 			return false;
 		wp_load_translations_early();
-		if ( $caller = $this->get_caller() )
+		if ( $caller = $this->get_caller() ) {
+			/* translators: 1: Database error message, 2: SQL query, 3: Name of the calling function */
 			$error_str = sprintf( __( 'WordPress database error %1$s for query %2$s made by %3$s' ), $str, $this->last_query, $caller );
-		else
+		} else {
+			/* translators: 1: Database error message, 2: SQL query */
 			$error_str = sprintf( __( 'WordPress database error %1$s for query %2$s' ), $str, $this->last_query );
+		}
 		error_log( $error_str );
 		// Are we showing errors?
 		if ( ! $this->show_errors )
 			return false;
 		// If there is an error then take note of it
 		if ( is_multisite() ) {
-			$msg = "WordPress database error: [$str]\n{$this->last_query}\n";
+			$msg = sprintf(
-			if ( defined( 'ERRORLOGFILE' ) )
+				"%s [%s]\n%s\n",
+				__( 'WordPress database error:' ),
+				$str,
+				$this->last_query
+			);
+			if ( defined( 'ERRORLOGFILE' ) ) {
 				error_log( $msg, 3, ERRORLOGFILE );
-			if ( defined( 'DIEONDBERROR' ) )
+			}
+			if ( defined( 'DIEONDBERROR' ) ) {
 				wp_die( $msg );
+			}
 		} else {
 			$str   = htmlspecialchars( $str, ENT_QUOTES );
 			$query = htmlspecialchars( $this->last_query, ENT_QUOTES );
-			print "<div id='error'>
+			printf(
-			<p class='wpdberror'><strong>WordPress database error:</strong> [$str]<br />
+				'<div id="error"><p class="wpdberror"><strong>%s</strong> [%s]<br /><code>%s</code></p></div>',
-			<code>$query</code></p>
+				__( 'WordPress database error:' ),
-			</div>";
+				$str,
+				$query
+			);
 		}
 	}
 	/**
 	 * Enables showing of database errors.
 	/**
 	 * Kill cached query results.
 	 *
 	 * @since 0.71
-	 * @return void
 	 */
 	public function flush() {
 		$this->last_result = array();
 		$this->col_info    = null;
 		$this->last_query  = null;
 	 *
 	 * @since 3.0.0
 	 * @since 3.9.0 $allow_bail parameter added.
 	 *
 	 * @param bool $allow_bail Optional. Allows the function to bail. Default true.
-	 * @return null|bool True with a successful connection, false on failure.
+	 * @return bool True with a successful connection, false on failure.
 	 */
 	public function db_connect( $allow_bail = true ) {
 		$this->is_mysql = true;
 		/*
 		 * Deprecated in 3.9+ when using MySQLi. No equivalent
 		 * $new_link parameter exists for mysqli_* functions.
 		$client_flags = defined( 'MYSQL_CLIENT_FLAGS' ) ? MYSQL_CLIENT_FLAGS : 0;
 		if ( $this->use_mysqli ) {
 			$this->dbh = mysqli_init();
-			// mysqli_real_connect doesn't support the host param including a port or socket
+			$host    = $this->dbhost;
-			// like mysql_connect does. This duplicates how mysql_connect detects a port and/or socket file.
+			$port    = null;
-			$port = null;
+			$socket  = null;
-			$socket = null;
+			$is_ipv6 = false;
-			$host = $this->dbhost;
-			$port_or_socket = strstr( $host, ':' );
+			if ( $host_data = $this->parse_db_host( $this->dbhost ) ) {
-			if ( ! empty( $port_or_socket ) ) {
+				list( $host, $port, $socket, $is_ipv6 ) = $host_data;
-				$host = substr( $host, 0, strpos( $host, ':' ) );
+			}
-				$port_or_socket = substr( $port_or_socket, 1 );
-				if ( 0 !== strpos( $port_or_socket, '/' ) ) {
+			/*
-					$port = intval( $port_or_socket );
+			 * If using the `mysqlnd` library, the IPv6 address needs to be
-					$maybe_socket = strstr( $port_or_socket, ':' );
+			 * enclosed in square brackets, whereas it doesn't while using the
-					if ( ! empty( $maybe_socket ) ) {
+			 * `libmysqlclient` library.
-						$socket = substr( $maybe_socket, 1 );
+			 * @see https://bugs.php.net/bug.php?id=67563
-					}
+			 */
-				} else {
+			if ( $is_ipv6 && extension_loaded( 'mysqlnd' ) ) {
-					$socket = $port_or_socket;
+				$host = "[$host]";
-				}
 			}
 			if ( WP_DEBUG ) {
 				mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags );
 			} else {
 			}
 			if ( $this->dbh->connect_errno ) {
 				$this->dbh = null;
-				/* It's possible ext/mysqli is misconfigured. Fall back to ext/mysql if:
+				/*
+				 * It's possible ext/mysqli is misconfigured. Fall back to ext/mysql if:
 		 		 *  - We haven't previously connected, and
 		 		 *  - WP_USE_EXT_MYSQL isn't set to false, and
 		 		 *  - ext/mysql is loaded.
 		 		 */
 				$attempt_fallback = true;
 					$attempt_fallback = false;
 				}
 				if ( $attempt_fallback ) {
 					$this->use_mysqli = false;
-					$this->db_connect();
+					return $this->db_connect( $allow_bail );
 				}
 			}
 		} else {
 			if ( WP_DEBUG ) {
 				$this->dbh = mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
 			if ( file_exists( WP_CONTENT_DIR . '/db-error.php' ) ) {
 				require_once( WP_CONTENT_DIR . '/db-error.php' );
 				die();
 			}
-			$this->bail( sprintf( __( "
+			$message = '<h1>' . __( 'Error establishing a database connection' ) . "</h1>\n";
-<h1>Error establishing a database connection</h1>
-<p>This either means that the username and password information in your <code>wp-config.php</code> file is incorrect or we can't contact the database server at <code>%s</code>. This could mean your host's database server is down.</p>
+			$message .= '<p>' . sprintf(
-<ul>
+				/* translators: 1: wp-config.php. 2: database host */
-	<li>Are you sure you have the correct username and password?</li>
+				__( 'This either means that the username and password information in your %1$s file is incorrect or we can&#8217;t contact the database server at %2$s. This could mean your host&#8217;s database server is down.' ),
-	<li>Are you sure that you have typed the correct hostname?</li>
+				'<code>wp-config.php</code>',
-	<li>Are you sure that the database server is running?</li>
+				'<code>' . htmlspecialchars( $this->dbhost, ENT_QUOTES ) . '</code>'
-</ul>
+			) . "</p>\n";
-<p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='https://wordpress.org/support/'>WordPress Support Forums</a>.</p>
-" ), htmlspecialchars( $this->dbhost, ENT_QUOTES ) ), 'db_connect_fail' );
+			$message .= "<ul>\n";
+			$message .= '<li>' . __( 'Are you sure you have the correct username and password?' ) . "</li>\n";
+			$message .= '<li>' . __( 'Are you sure that you have typed the correct hostname?' ) . "</li>\n";
+			$message .= '<li>' . __( 'Are you sure that the database server is running?' ) . "</li>\n";
+			$message .= "</ul>\n";
+			$message .= '<p>' . sprintf(
+				/* translators: %s: support forums URL */
+				__( 'If you&#8217;re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href="%s">WordPress Support Forums</a>.' ),
+				__( 'https://wordpress.org/support/' )
+			) . "</p>\n";
+			$this->bail( $message, 'db_connect_fail' );
 			return false;
 		} elseif ( $this->dbh ) {
 			if ( ! $this->has_connected ) {
 				$this->init_charset();
 		return false;
 	}
 	/**
-	 * Check that the connection to the database is still up. If not, try to reconnect.
+	 * Parse the DB_HOST setting to interpret it for mysqli_real_connect.
+	 *
+	 * mysqli_real_connect doesn't support the host param including a port or
+	 * socket like mysql_connect does. This duplicates how mysql_connect detects
+	 * a port and/or socket file.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param string $host The DB_HOST setting to parse.
+	 * @return array|bool Array containing the host, the port, the socket and whether
+	 *                    it is an IPv6 address, in that order. If $host couldn't be parsed,
+	 *                    returns false.
+	 */
+	public function parse_db_host( $host ) {
+		$port    = null;
+		$socket  = null;
+		$is_ipv6 = false;
+		// First peel off the socket parameter from the right, if it exists.
+		$socket_pos = strpos( $host, ':/' );
+		if ( $socket_pos !== false ) {
+			$socket = substr( $host, $socket_pos + 1 );
+			$host = substr( $host, 0, $socket_pos );
+		}
+		// We need to check for an IPv6 address first.
+		// An IPv6 address will always contain at least two colons.
+		if ( substr_count( $host, ':' ) > 1 ) {
+			$pattern = '#^(?:\[)?(?P<host>[0-9a-fA-F:]+)(?:\]:(?P<port>[\d]+))?#';
+			$is_ipv6 = true;
+		} else {
+			// We seem to be dealing with an IPv4 address.
+			$pattern = '#^(?P<host>[^:/]*)(?::(?P<port>[\d]+))?#';
+		}
+		$matches = array();
+		$result = preg_match( $pattern, $host, $matches );
+		if ( 1 !== $result ) {
+			// Couldn't parse the address, bail.
+			return false;
+		}
+		$host = '';
+		foreach ( array( 'host', 'port' ) as $component ) {
+			if ( ! empty( $matches[ $component ] ) ) {
+				$$component = $matches[ $component ];
+			}
+		}
+		return array( $host, $port, $socket, $is_ipv6 );
+	}
+	/**
+	 * Checks that the connection to the database is still up. If not, try to reconnect.
 	 *
 	 * If this function is unable to reconnect, it will forcibly die, or if after the
-	 * the template_redirect hook has been fired, return false instead.
+	 * the {@see 'template_redirect'} hook has been fired, return false instead.
 	 *
 	 * If $allow_bail is false, the lack of database connection will need
 	 * to be handled manually.
 	 *
 	 * @since 3.9.0
 	 *
 	 * @param bool $allow_bail Optional. Allows the function to bail. Default true.
-	 * @return bool|null True if the connection is up.
+	 * @return bool|void True if the connection is up.
 	 */
 	public function check_connection( $allow_bail = true ) {
 		if ( $this->use_mysqli ) {
-			if ( @mysqli_ping( $this->dbh ) ) {
+			if ( ! empty( $this->dbh ) && mysqli_ping( $this->dbh ) ) {
 				return true;
 			}
 		} else {
-			if ( @mysql_ping( $this->dbh ) ) {
+			if ( ! empty( $this->dbh ) && mysql_ping( $this->dbh ) ) {
 				return true;
 			}
 		}
 		$error_reporting = false;
 		if ( ! $allow_bail ) {
 			return false;
 		}
+		wp_load_translations_early();
+		$message = '<h1>' . __( 'Error reconnecting to the database' ) . "</h1>\n";
+		$message .= '<p>' . sprintf(
+			/* translators: %s: database host */
+			__( 'This means that we lost contact with the database server at %s. This could mean your host&#8217;s database server is down.' ),
+			'<code>' . htmlspecialchars( $this->dbhost, ENT_QUOTES ) . '</code>'
+		) . "</p>\n";
+		$message .= "<ul>\n";
+		$message .= '<li>' . __( 'Are you sure that the database server is running?' ) . "</li>\n";
+		$message .= '<li>' . __( 'Are you sure that the database server is not under particularly heavy load?' ) . "</li>\n";
+		$message .= "</ul>\n";
+		$message .= '<p>' . sprintf(
+			/* translators: %s: support forums URL */
+			__( 'If you&#8217;re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href="%s">WordPress Support Forums</a>.' ),
+			__( 'https://wordpress.org/support/' )
+		) . "</p>\n";
 		// We weren't able to reconnect, so we better bail.
-		$this->bail( sprintf( ( "
+		$this->bail( $message, 'db_connect_fail' );
-<h1>Error reconnecting to the database</h1>
-<p>This means that we lost contact with the database server at <code>%s</code>. This could mean your host's database server is down.</p>
-<ul>
-	<li>Are you sure that the database server is running?</li>
-	<li>Are you sure that the database server is not under particularly heavy load?</li>
-</ul>
-<p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='https://wordpress.org/support/'>WordPress Support Forums</a>.</p>
-" ), htmlspecialchars( $this->dbhost, ENT_QUOTES ) ), 'db_connect_fail' );
 		// Call dead_db() if bail didn't die, because this database is no more. It has ceased to be (at least temporarily).
 		dead_db();
 	}
 			$this->check_current_query = true;
 			return false;
 		}
 		/**
-		 * Filter the database query.
+		 * Filters the database query.
 		 *
 		 * Some queries are made before the plugins have been loaded,
 		 * and thus cannot be filtered with this method.
 		 *
 		 * @since 2.1.0
 			}
 		}
 		$this->check_current_query = true;
-		// Keep track of the last query for debug..
+		// Keep track of the last query for debug.
 		$this->last_query = $query;
 		$this->_do_query( $query );
-		// MySQL server has gone away, try to reconnect
+		// MySQL server has gone away, try to reconnect.
 		$mysql_errno = 0;
 		if ( ! empty( $this->dbh ) ) {
 			if ( $this->use_mysqli ) {
-				$mysql_errno = mysqli_errno( $this->dbh );
+				if ( $this->dbh instanceof mysqli ) {
+					$mysql_errno = mysqli_errno( $this->dbh );
+				} else {
+					// $dbh is defined, but isn't a real connection.
+					// Something has gone horribly wrong, let's try a reconnect.
+					$mysql_errno = 2006;
+				}
 			} else {
-				$mysql_errno = mysql_errno( $this->dbh );
+				if ( is_resource( $this->dbh ) ) {
+					$mysql_errno = mysql_errno( $this->dbh );
+				} else {
+					$mysql_errno = 2006;
+				}
 			}
 		}
 		if ( empty( $this->dbh ) || 2006 == $mysql_errno ) {
 			if ( $this->check_connection() ) {
 				$this->insert_id = 0;
 				return false;
 			}
 		}
-		// If there is an error then take note of it..
+		// If there is an error then take note of it.
 		if ( $this->use_mysqli ) {
-			$this->last_error = mysqli_error( $this->dbh );
+			if ( $this->dbh instanceof mysqli ) {
+				$this->last_error = mysqli_error( $this->dbh );
+			} else {
+				$this->last_error = __( 'Unable to retrieve the error message from MySQL' );
+			}
 		} else {
-			$this->last_error = mysql_error( $this->dbh );
+			if ( is_resource( $this->dbh ) ) {
+				$this->last_error = mysql_error( $this->dbh );
+			} else {
+				$this->last_error = __( 'Unable to retrieve the error message from MySQL' );
+			}
 		}
 		if ( $this->last_error ) {
 			// Clear insert_id on a subsequent failed insert.
 			if ( $this->insert_id && preg_match( '/^\s*(insert|replace)\s/i', $query ) )
 			// Return number of rows affected
 			$return_val = $this->rows_affected;
 		} else {
 			$num_rows = 0;
 			if ( $this->use_mysqli && $this->result instanceof mysqli_result ) {
-				while ( $row = @mysqli_fetch_object( $this->result ) ) {
+				while ( $row = mysqli_fetch_object( $this->result ) ) {
 					$this->last_result[$num_rows] = $row;
 					$num_rows++;
 				}
 			} elseif ( is_resource( $this->result ) ) {
-				while ( $row = @mysql_fetch_object( $this->result ) ) {
+				while ( $row = mysql_fetch_object( $this->result ) ) {
 					$this->last_result[$num_rows] = $row;
 					$num_rows++;
 				}
 			}
 	/**
 	 * Internal function to perform the mysql_query() call.
 	 *
 	 * @since 3.9.0
 	 *
-	 * @access private
 	 * @see wpdb::query()
 	 *
 	 * @param string $query The query to run.
 	 */
 	private function _do_query( $query ) {
 		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
 			$this->timer_start();
 		}
-		if ( $this->use_mysqli ) {
+		if ( ! empty( $this->dbh ) && $this->use_mysqli ) {
-			$this->result = @mysqli_query( $this->dbh, $query );
+			$this->result = mysqli_query( $this->dbh, $query );
-		} else {
+		} elseif ( ! empty( $this->dbh ) ) {
-			$this->result = @mysql_query( $query, $this->dbh );
+			$this->result = mysql_query( $query, $this->dbh );
 		}
 		$this->num_queries++;
 		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
 			$this->queries[] = array( $query, $this->timer_stop(), $this->get_caller() );
 		}
+	}
+	/**
+	 * Generates and returns a placeholder escape string for use in queries returned by ::prepare().
+	 *
+	 * @since 4.8.3
+	 *
+	 * @return string String to escape placeholders.
+	 */
+	public function placeholder_escape() {
+		static $placeholder;
+		if ( ! $placeholder ) {
+			// If ext/hash is not present, compat.php's hash_hmac() does not support sha256.
+			$algo = function_exists( 'hash' ) ? 'sha256' : 'sha1';
+			// Old WP installs may not have AUTH_SALT defined.
+			$salt = defined( 'AUTH_SALT' ) && AUTH_SALT ? AUTH_SALT : (string) rand();
+			$placeholder = '{' . hash_hmac( $algo, uniqid( $salt, true ), $salt ) . '}';
+		}
+		/*
+		 * Add the filter to remove the placeholder escaper. Uses priority 0, so that anything
+		 * else attached to this filter will recieve the query with the placeholder string removed.
+		 */
+		if ( ! has_filter( 'query', array( $this, 'remove_placeholder_escape' ) ) ) {
+			add_filter( 'query', array( $this, 'remove_placeholder_escape' ), 0 );
+		}
+		return $placeholder;
+	}
+	/**
+	 * Adds a placeholder escape string, to escape anything that resembles a printf() placeholder.
+	 *
+	 * @since 4.8.3
+	 *
+	 * @param string $query The query to escape.
+	 * @return string The query with the placeholder escape string inserted where necessary.
+	 */
+	public function add_placeholder_escape( $query ) {
+		/*
+		 * To prevent returning anything that even vaguely resembles a placeholder,
+		 * we clobber every % we can find.
+		 */
+		return str_replace( '%', $this->placeholder_escape(), $query );
+	}
+	/**
+	 * Removes the placeholder escape strings from a query.
+	 *
+	 * @since 4.8.3
+	 *
+	 * @param string $query The query from which the placeholder will be removed.
+	 * @return string The query with the placeholder removed.
+	 */
+	public function remove_placeholder_escape( $query ) {
+		return str_replace( $this->placeholder_escape(), '%', $query );
 	}
 	/**
 	 * Insert a row into a table.
 	 *
 	 * @since 2.5.0
 	 * @see wpdb::prepare()
 	 * @see wpdb::$field_types
 	 * @see wp_set_wpdb_vars()
 	 *
-	 * @param string $table table name
+	 * @param string       $table  Table name
-	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
+	 * @param array        $data   Data to insert (in column => value pairs).
-	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
+	 *                             Both $data columns and $data values should be "raw" (neither should be SQL escaped).
-	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 *                             Sending a null value will cause the column to be set to NULL - the corresponding format is ignored in this case.
+	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data.
+	 *                             If string, that format will be used for all of the values in $data.
+	 *                             A format is one of '%d', '%f', '%s' (integer, float, string).
+	 *                             If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
 	 * @return int|false The number of rows inserted, or false on error.
 	 */
 	public function insert( $table, $data, $format = null ) {
 		return $this->_insert_replace_helper( $table, $data, $format, 'INSERT' );
 	}
 	 * @since 3.0.0
 	 * @see wpdb::prepare()
 	 * @see wpdb::$field_types
 	 * @see wp_set_wpdb_vars()
 	 *
-	 * @param string $table table name
+	 * @param string       $table  Table name
-	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
+	 * @param array        $data   Data to insert (in column => value pairs).
-	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
+	 *                             Both $data columns and $data values should be "raw" (neither should be SQL escaped).
-	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 *                             Sending a null value will cause the column to be set to NULL - the corresponding format is ignored in this case.
+	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data.
+	 *                             If string, that format will be used for all of the values in $data.
+	 *                             A format is one of '%d', '%f', '%s' (integer, float, string).
+	 *                             If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
 	 * @return int|false The number of rows affected, or false on error.
 	 */
 	public function replace( $table, $data, $format = null ) {
 		return $this->_insert_replace_helper( $table, $data, $format, 'REPLACE' );
 	}
 	/**
 	 * Helper function for insert and replace.
 	 *
 	 * Runs an insert or replace query based on $type argument.
 	 *
-	 * @access private
 	 * @since 3.0.0
 	 * @see wpdb::prepare()
 	 * @see wpdb::$field_types
 	 * @see wp_set_wpdb_vars()
 	 *
-	 * @param string $table table name
+	 * @param string       $table  Table name
-	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
+	 * @param array        $data   Data to insert (in column => value pairs).
-	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
+	 *                             Both $data columns and $data values should be "raw" (neither should be SQL escaped).
-	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 *                             Sending a null value will cause the column to be set to NULL - the corresponding format is ignored in this case.
-	 * @param string $type Optional. What type of operation is this? INSERT or REPLACE. Defaults to INSERT.
+	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data.
+	 *                             If string, that format will be used for all of the values in $data.
+	 *                             A format is one of '%d', '%f', '%s' (integer, float, string).
+	 *                             If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 * @param string $type         Optional. What type of operation is this? INSERT or REPLACE. Defaults to INSERT.
 	 * @return int|false The number of rows affected, or false on error.
 	 */
 	function _insert_replace_helper( $table, $data, $format = null, $type = 'INSERT' ) {
 		$this->insert_id = 0;
 			return false;
 		}
 		$formats = $values = array();
 		foreach ( $data as $value ) {
+			if ( is_null( $value['value'] ) ) {
+				$formats[] = 'NULL';
+				continue;
+			}
 			$formats[] = $value['format'];
 			$values[]  = $value['value'];
 		}
 		$fields  = '`' . implode( '`, `', array_keys( $data ) ) . '`';
 	 * @since 2.5.0
 	 * @see wpdb::prepare()
 	 * @see wpdb::$field_types
 	 * @see wp_set_wpdb_vars()
 	 *
-	 * @param string $table table name
+	 * @param string       $table        Table name
-	 * @param array $data Data to update (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
+	 * @param array        $data         Data to update (in column => value pairs).
-	 * @param array $where A named array of WHERE clauses (in column => value pairs). Multiple clauses will be joined with ANDs. Both $where columns and $where values should be "raw".
+	 *                                   Both $data columns and $data values should be "raw" (neither should be SQL escaped).
-	 * @param array|string $format Optional. An array of formats to be mapped to each of the values in $data. If string, that format will be used for all of the values in $data.
+	 *                                   Sending a null value will cause the column to be set to NULL - the corresponding
-	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 *                                   format is ignored in this case.
-	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where. If string, that format will be used for all of the items in $where. A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $where will be treated as strings.
+	 * @param array        $where        A named array of WHERE clauses (in column => value pairs).
+	 *                                   Multiple clauses will be joined with ANDs.
+	 *                                   Both $where columns and $where values should be "raw".
+	 *                                   Sending a null value will create an IS NULL comparison - the corresponding format will be ignored in this case.
+	 * @param array|string $format       Optional. An array of formats to be mapped to each of the values in $data.
+	 *                                   If string, that format will be used for all of the values in $data.
+	 *                                   A format is one of '%d', '%f', '%s' (integer, float, string).
+	 *                                   If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where.
+	 *                                   If string, that format will be used for all of the items in $where.
+	 *                                   A format is one of '%d', '%f', '%s' (integer, float, string).
+	 *                                   If omitted, all values in $where will be treated as strings.
 	 * @return int|false The number of rows updated, or false on error.
 	 */
 	public function update( $table, $data, $where, $format = null, $where_format = null ) {
 		if ( ! is_array( $data ) || ! is_array( $where ) ) {
 			return false;
 			return false;
 		}
 		$fields = $conditions = $values = array();
 		foreach ( $data as $field => $value ) {
+			if ( is_null( $value['value'] ) ) {
+				$fields[] = "`$field` = NULL";
+				continue;
+			}
 			$fields[] = "`$field` = " . $value['format'];
 			$values[] = $value['value'];
 		}
 		foreach ( $where as $field => $value ) {
+			if ( is_null( $value['value'] ) ) {
+				$conditions[] = "`$field` IS NULL";
+				continue;
+			}
 			$conditions[] = "`$field` = " . $value['format'];
 			$values[] = $value['value'];
 		}
 		$fields = implode( ', ', $fields );
 	 * @since 3.4.0
 	 * @see wpdb::prepare()
 	 * @see wpdb::$field_types
 	 * @see wp_set_wpdb_vars()
 	 *
-	 * @param string $table table name
+	 * @param string       $table        Table name
-	 * @param array $where A named array of WHERE clauses (in column => value pairs). Multiple clauses will be joined with ANDs. Both $where columns and $where values should be "raw".
+	 * @param array        $where        A named array of WHERE clauses (in column => value pairs).
-	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where. If string, that format will be used for all of the items in $where. A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $where will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 *                                   Multiple clauses will be joined with ANDs.
+	 *                                   Both $where columns and $where values should be "raw".
+	 *                                   Sending a null value will create an IS NULL comparison - the corresponding format will be ignored in this case.
+	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where.
+	 *                                   If string, that format will be used for all of the items in $where.
+	 *                                   A format is one of '%d', '%f', '%s' (integer, float, string).
+	 *                                   If omitted, all values in $where will be treated as strings unless otherwise specified in wpdb::$field_types.
 	 * @return int|false The number of rows updated, or false on error.
 	 */
 	public function delete( $table, $where, $where_format = null ) {
 		if ( ! is_array( $where ) ) {
 			return false;
 			return false;
 		}
 		$conditions = $values = array();
 		foreach ( $where as $field => $value ) {
+			if ( is_null( $value['value'] ) ) {
+				$conditions[] = "`$field` IS NULL";
+				continue;
+			}
 			$conditions[] = "`$field` = " . $value['format'];
 			$values[] = $value['value'];
 		}
 		$conditions = implode( ' AND ', $conditions );
 	 * each value with a format. Then it determines the charset of that field,
 	 * using that to determine if any invalid text would be stripped. If text is
 	 * stripped, then field processing is rejected and the query fails.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param string $table  Table name.
 	 * @param array  $data   Field/value pair.
 	 * @param mixed  $format Format for each field.
-	 * @return array|bool Returns an array of fields that contain paired values
+	 * @return array|false Returns an array of fields that contain paired values
 	 *                    and formats. Returns false for invalid values.
 	 */
 	protected function process_fields( $table, $data, $format ) {
 		$data = $this->process_field_formats( $data, $format );
 		if ( false === $data ) {
 	/**
 	 * Prepares arrays of value/format pairs as passed to wpdb CRUD methods.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param array $data   Array of fields to values.
 	 * @param mixed $format Formats to be mapped to the values in $data.
 	 * @return array Array, keyed by field names with values being an array
 	 *               of 'value' and 'format' keys.
 	/**
 	 * Adds field charsets to field/value/format arrays generated by
 	 * the wpdb::process_field_formats() method.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param array  $data  As it comes from the wpdb::process_field_formats() method.
 	 * @param string $table Table name.
-	 * @return The same array as $data with additional 'charset' keys.
+	 * @return array|false The same array as $data with additional 'charset' keys.
 	 */
 	protected function process_field_charsets( $data, $table ) {
 		foreach ( $data as $field => $value ) {
 			if ( '%d' === $value['format'] || '%f' === $value['format'] ) {
-				// We can skip this field if we know it isn't a string.
+				/*
-				// This checks %d/%f versus ! %s because it's sprintf() could take more.
+				 * We can skip this field if we know it isn't a string.
+				 * This checks %d/%f versus ! %s because its sprintf() could take more.
+				 */
 				$value['charset'] = false;
 			} else {
 				$value['charset'] = $this->get_col_charset( $table, $field );
 				if ( is_wp_error( $value['charset'] ) ) {
 					return false;
 	/**
 	 * For string fields, record the maximum string length that field can safely save.
 	 *
 	 * @since 4.2.1
-	 * @access protected
 	 *
 	 * @param array  $data  As it comes from the wpdb::process_field_charsets() method.
 	 * @param string $table Table name.
-	 * @return array|False The same array as $data with additional 'length' keys, or false if
+	 * @return array|false The same array as $data with additional 'length' keys, or false if
 	 *                     any of the values were too long for their corresponding field.
 	 */
 	protected function process_field_lengths( $data, $table ) {
 		foreach ( $data as $field => $value ) {
 			if ( '%d' === $value['format'] || '%f' === $value['format'] ) {
-				// We can skip this field if we know it isn't a string.
+				/*
-				// This checks %d/%f versus ! %s because it's sprintf() could take more.
+				 * We can skip this field if we know it isn't a string.
+				 * This checks %d/%f versus ! %s because its sprintf() could take more.
+				 */
 				$value['length'] = false;
 			} else {
 				$value['length'] = $this->get_col_length( $table, $field );
 				if ( is_wp_error( $value['length'] ) ) {
 					return false;
 	 * If $query is null, this function returns the value in the specified column and row from the previous SQL result.
 	 *
 	 * @since 0.71
 	 *
 	 * @param string|null $query Optional. SQL query. Defaults to null, use the result from the previous query.
-	 * @param int $x Optional. Column of value to return. Indexed from 0.
+	 * @param int         $x     Optional. Column of value to return. Indexed from 0.
-	 * @param int $y Optional. Row of value to return. Indexed from 0.
+	 * @param int         $y     Optional. Row of value to return. Indexed from 0.
 	 * @return string|null Database query result (as string), or null on failure
 	 */
 	public function get_var( $query = null, $x = 0, $y = 0 ) {
 		$this->func_call = "\$db->get_var(\"$query\", $x, $y)";
-		if ( $this->check_safe_collation( $query ) ) {
+		if ( $this->check_current_query && $this->check_safe_collation( $query ) ) {
 			$this->check_current_query = false;
 		}
 		if ( $query ) {
 			$this->query( $query );
 	 *
 	 * Executes a SQL query and returns the row from the SQL result.
 	 *
 	 * @since 0.71
 	 *
-	 * @param string|null $query SQL query.
+	 * @param string|null $query  SQL query.
-	 * @param string $output Optional. one of ARRAY_A | ARRAY_N | OBJECT constants. Return an associative array (column => value, ...),
+	 * @param string      $output Optional. The required return type. One of OBJECT, ARRAY_A, or ARRAY_N, which correspond to
-	 * 	a numerically indexed array (0 => value, ...) or an object ( ->column = value ), respectively.
+	 *                            an stdClass object, an associative array, or a numeric array, respectively. Default OBJECT.
-	 * @param int $y Optional. Row to return. Indexed from 0.
+	 * @param int         $y      Optional. Row to return. Indexed from 0.
-	 * @return mixed Database query result in format specified by $output or null on failure
+	 * @return array|object|null|void Database query result in format specified by $output or null on failure
 	 */
 	public function get_row( $query = null, $output = OBJECT, $y = 0 ) {
 		$this->func_call = "\$db->get_row(\"$query\",$output,$y)";
-		if ( $this->check_safe_collation( $query ) ) {
+		if ( $this->check_current_query && $this->check_safe_collation( $query ) ) {
 			$this->check_current_query = false;
 		}
 		if ( $query ) {
 			$this->query( $query );
 	 * If $query is null, this function returns the specified column from the previous SQL result.
 	 *
 	 * @since 0.71
 	 *
 	 * @param string|null $query Optional. SQL query. Defaults to previous query.
-	 * @param int $x Optional. Column to return. Indexed from 0.
+	 * @param int         $x     Optional. Column to return. Indexed from 0.
 	 * @return array Database query result. Array indexed from 0 by SQL result row number.
 	 */
 	public function get_col( $query = null , $x = 0 ) {
-		if ( $this->check_safe_collation( $query ) ) {
+		if ( $this->check_current_query && $this->check_safe_collation( $query ) ) {
 			$this->check_current_query = false;
 		}
 		if ( $query ) {
 			$this->query( $query );
 	 *
 	 * Executes a SQL query and returns the entire SQL result.
 	 *
 	 * @since 0.71
 	 *
-	 * @param string $query SQL query.
+	 * @param string $query  SQL query.
-	 * @param string $output Optional. Any of ARRAY_A | ARRAY_N | OBJECT | OBJECT_K constants. With one of the first three, return an array of rows indexed from 0 by SQL result row number.
+	 * @param string $output Optional. Any of ARRAY_A | ARRAY_N | OBJECT | OBJECT_K constants.
-	 * 	Each row is an associative array (column => value, ...), a numerically indexed array (0 => value, ...), or an object. ( ->column = value ), respectively.
+	 *                       With one of the first three, return an array of rows indexed from 0 by SQL result row number.
-	 * 	With OBJECT_K, return an associative array of row objects keyed by the value of each row's first column's value. Duplicate keys are discarded.
+	 *                       Each row is an associative array (column => value, ...), a numerically indexed array (0 => value, ...), or an object. ( ->column = value ), respectively.
-	 * @return mixed Database query results
+	 *                       With OBJECT_K, return an associative array of row objects keyed by the value of each row's first column's value.
+	 *                       Duplicate keys are discarded.
+	 * @return array|object|null Database query results
 	 */
 	public function get_results( $query = null, $output = OBJECT ) {
 		$this->func_call = "\$db->get_results(\"$query\", $output)";
-		if ( $this->check_safe_collation( $query ) ) {
+		if ( $this->check_current_query && $this->check_safe_collation( $query ) ) {
 			$this->check_current_query = false;
 		}
 		if ( $query ) {
 			$this->query( $query );
 			}
 			return $new_array;
 		} elseif ( $output == ARRAY_A || $output == ARRAY_N ) {
 			// Return an integer-keyed array of...
 			if ( $this->last_result ) {
-				foreach( (array) $this->last_result as $row ) {
+				foreach ( (array) $this->last_result as $row ) {
 					if ( $output == ARRAY_N ) {
 						// ...integer-keyed row arrays
 						$new_array[] = array_values( get_object_vars( $row ) );
 					} else {
 						// ...column name-keyed row arrays
 	/**
 	 * Retrieves the character set for the given table.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param string $table Table name.
 	 * @return string|WP_Error Table character set, WP_Error object if it couldn't be found.
 	 */
 	protected function get_table_charset( $table ) {
 		$tablekey = strtolower( $table );
 		/**
-		 * Filter the table charset value before the DB is checked.
+		 * Filters the table charset value before the DB is checked.
 		 *
 		 * Passing a non-null value to the filter will effectively short-circuit
 		 * checking the DB for the charset, returning that value instead.
 		 *
 		 * @since 4.2.0
 	/**
 	 * Retrieves the character set for the given column.
 	 *
 	 * @since 4.2.0
-	 * @access public
 	 *
 	 * @param string $table  Table name.
 	 * @param string $column Column name.
-	 * @return mixed Column character set as a string. False if the column has no
+	 * @return string|false|WP_Error Column character set as a string. False if the column has no
-	 *               character set. WP_Error object if there was an error.
+	 *                               character set. WP_Error object if there was an error.
 	 */
 	public function get_col_charset( $table, $column ) {
 		$tablekey = strtolower( $table );
 		$columnkey = strtolower( $column );
 		/**
-		 * Filter the column charset value before the DB is checked.
+		 * Filters the column charset value before the DB is checked.
 		 *
 		 * Passing a non-null value to the filter will short-circuit
 		 * checking the DB for the charset, returning that value instead.
 		 *
 		 * @since 4.2.0
 		if ( null !== $charset ) {
 			return $charset;
 		}
 		// Skip this entirely if this isn't a MySQL database.
-		if ( false === $this->is_mysql ) {
+		if ( empty( $this->is_mysql ) ) {
 			return false;
 		}
 		if ( empty( $this->table_charset[ $tablekey ] ) ) {
 			// This primes column information for us.
 	/**
 	 * Retrieve the maximum string length allowed in a given column.
 	 * The length may either be specified as a byte length or a character length.
 	 *
 	 * @since 4.2.1
-	 * @access public
 	 *
 	 * @param string $table  Table name.
 	 * @param string $column Column name.
-	 * @return mixed array( 'length' => (int), 'type' => 'byte' | 'char' )
+	 * @return array|false|WP_Error array( 'length' => (int), 'type' => 'byte' | 'char' )
-	 *               false if the column has no length (for example, numeric column)
+	 *                              false if the column has no length (for example, numeric column)
-	 *               WP_Error object if there was an error.
+	 *                              WP_Error object if there was an error.
 	 */
 	public function get_col_length( $table, $column ) {
 		$tablekey = strtolower( $table );
 		$columnkey = strtolower( $column );
 		// Skip this entirely if this isn't a MySQL database.
-		if ( false === $this->is_mysql ) {
+		if ( empty( $this->is_mysql ) ) {
 			return false;
 		}
 		if ( empty( $this->col_meta[ $tablekey ] ) ) {
 			// This primes column information for us.
 			case 'varchar':
 				return array(
 					'type'   => 'char',
 					'length' => (int) $length,
 				);
-				break;
 			case 'binary':
 			case 'varbinary':
 				return array(
 					'type'   => 'byte',
 					'length' => (int) $length,
 				);
-				break;
 			case 'tinyblob':
 			case 'tinytext':
 				return array(
 					'type'   => 'byte',
 					'length' => 255,        // 2^8 - 1
 				);
-				break;
 			case 'blob':
 			case 'text':
 				return array(
 					'type'   => 'byte',
 					'length' => 65535,      // 2^16 - 1
 				);
-				break;
 			case 'mediumblob':
 			case 'mediumtext':
 				return array(
 					'type'   => 'byte',
 					'length' => 16777215,   // 2^24 - 1
 				);
-				break;
 			case 'longblob':
 			case 'longtext':
 				return array(
 					'type'   => 'byte',
 					'length' => 4294967295, // 2^32 - 1
 				);
-				break;
 			default:
 				return false;
 		}
-		return false;
 	}
 	/**
 	 * Check if a string is ASCII.
 	 *
 	 * The negative regex is faster for non-ASCII strings, as it allows
 	 * the search to finish as soon as it encounters a non-ASCII character.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param string $string String to check.
 	 * @return bool True if ASCII, false if not.
 	 */
 	protected function check_ascii( $string ) {
 	/**
 	 * Check if the query is accessing a collation considered safe on the current version of MySQL.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param string $query The query to check.
 	 * @return bool True if the collation is safe, false if it isn't.
 	 */
 	protected function check_safe_collation( $query ) {
 		if ( empty( $this->col_meta[ $table ] ) ) {
 			return false;
 		}
 		// If any of the columns don't have one of these collations, it needs more sanity checking.
-		foreach( $this->col_meta[ $table ] as $col ) {
+		foreach ( $this->col_meta[ $table ] as $col ) {
 			if ( empty( $col->Collation ) ) {
 				continue;
 			}
 			if ( ! in_array( $col->Collation, array( 'utf8_general_ci', 'utf8_bin', 'utf8mb4_general_ci', 'utf8mb4_bin' ), true ) ) {
 	/**
 	 * Strips any invalid characters based on value/charset pairs.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param array $data Array of value arrays. Each value array has the keys
 	 *                    'value' and 'charset'. An optional 'ascii' key can be
 	 *                    set to false to avoid redundant ASCII checks.
 	 * @return array|WP_Error The $data parameter, with invalid characters removed from
 		foreach ( $data as &$value ) {
 			$charset = $value['charset'];
 			if ( is_array( $value['length'] ) ) {
 				$length = $value['length']['length'];
+				$truncate_by_byte_length = 'byte' === $value['length']['type'];
 			} else {
 				$length = false;
+				// Since we have no length, we'll never truncate.
+				// Initialize the variable to false. true would take us
+				// through an unnecessary (for this case) codepath below.
+				$truncate_by_byte_length = false;
 			}
 			// There's no charset to work with.
 			if ( false === $charset ) {
 				continue;
 			// Column isn't a string.
 			if ( ! is_string( $value['value'] ) ) {
 				continue;
 			}
-			$truncate_by_byte_length = 'byte' === $value['length']['type'];
 			$needs_validation = true;
 			if (
 				// latin1 can store any byte sequence
 				'latin1' === $charset
 		if ( $db_check_string ) {
 			$queries = array();
 			foreach ( $data as $col => $value ) {
 				if ( ! empty( $value['db'] ) ) {
-					if ( ! isset( $queries[ $value['charset'] ] ) ) {
-						$queries[ $value['charset'] ] = array();
-					}
 					// We're going to need to truncate by characters or bytes, depending on the length value we have.
 					if ( 'byte' === $value['length']['type'] ) {
-						// Split the CONVERT() calls by charset, so we can make sure the connection is right
+						// Using binary causes LEFT() to truncate by bytes.
-						$queries[ $value['charset'] ][ $col ] = $this->prepare( "CONVERT( LEFT( CONVERT( %s USING binary ), %d ) USING {$value['charset']} )", $value['value'], $value['length']['length'] );
+						$charset = 'binary';
 					} else {
-						$queries[ $value['charset'] ][ $col ] = $this->prepare( "LEFT( CONVERT( %s USING {$value['charset']} ), %d )", $value['value'], $value['length']['length'] );
+						$charset = $value['charset'];
+					}
+					if ( $this->charset ) {
+						$connection_charset = $this->charset;
+					} else {
+						if ( $this->use_mysqli ) {
+							$connection_charset = mysqli_character_set_name( $this->dbh );
+						} else {
+							$connection_charset = mysql_client_encoding();
+						}
+					}
+					if ( is_array( $value['length'] ) ) {
+						$length = sprintf( '%.0f', $value['length']['length'] );
+						$queries[ $col ] = $this->prepare( "CONVERT( LEFT( CONVERT( %s USING $charset ), $length ) USING $connection_charset )", $value['value'] );
+					} else if ( 'binary' !== $charset ) {
+						// If we don't have a length, there's no need to convert binary - it will always return the same result.
+						$queries[ $col ] = $this->prepare( "CONVERT( CONVERT( %s USING $charset ) USING $connection_charset )", $value['value'] );
 					}
 					unset( $data[ $col ]['db'] );
 				}
 			}
-			$connection_charset = $this->charset;
+			$sql = array();
-			foreach ( $queries as $charset => $query ) {
+			foreach ( $queries as $column => $query ) {
 				if ( ! $query ) {
 					continue;
 				}
-				// Change the charset to match the string(s) we're converting
+				$sql[] = $query . " AS x_$column";
-				if ( $charset !== $connection_charset ) {
+			}
-					$connection_charset = $charset;
-					$this->set_charset( $this->dbh, $charset );
+			$this->check_current_query = false;
-				}
+			$row = $this->get_row( "SELECT " . implode( ', ', $sql ), ARRAY_A );
+			if ( ! $row ) {
-				$this->check_current_query = false;
+				return new WP_Error( 'wpdb_strip_invalid_text_failure' );
+			}
-				$sql = array();
-				foreach ( $query as $column => $column_query ) {
+			foreach ( array_keys( $data ) as $column ) {
-					$sql[] = $column_query . " AS x_$column";
+				if ( isset( $row["x_$column"] ) ) {
-				}
-				$row = $this->get_row( "SELECT " . implode( ', ', $sql ), ARRAY_A );
-				if ( ! $row ) {
-					$this->set_charset( $this->dbh, $connection_charset );
-					return new WP_Error( 'wpdb_strip_invalid_text_failure' );
-				}
-				foreach ( array_keys( $query ) as $column ) {
 					$data[ $column ]['value'] = $row["x_$column"];
 				}
 			}
-			// Don't forget to change the charset back!
-			if ( $connection_charset !== $this->charset ) {
-				$this->set_charset( $this->dbh );
-			}
 		}
 		return $data;
 	}
 	/**
 	 * Strips any invalid characters from the query.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param string $query Query to convert.
 	 * @return string|WP_Error The converted query, or a WP_Error object if the conversion fails.
 	 */
 	protected function strip_invalid_text_from_query( $query ) {
 	/**
 	 * Strips any invalid characters from the string for a given table and column.
 	 *
 	 * @since 4.2.0
-	 * @access public
 	 *
 	 * @param string $table  Table name.
 	 * @param string $column Column name.
 	 * @param string $value  The text to check.
 	 * @return string|WP_Error The converted string, or a WP_Error object if the conversion fails.
 	/**
 	 * Find the first table name referenced in a query.
 	 *
 	 * @since 4.2.0
-	 * @access protected
 	 *
 	 * @param string $query The query to search.
 	 * @return string|false $table The table name found, or false if a table couldn't be found.
 	 */
 	protected function get_table_from_query( $query ) {
 		$query = rtrim( $query, ';/-#' );
 		// Allow (select...) union [...] style queries. Use the first query's table name.
 		$query = ltrim( $query, "\r\n\t (" );
-		/*
+		// Strip everything between parentheses except nested selects.
-		 * Strip everything between parentheses except nested selects and use only 1,000
+		$query = preg_replace( '/\((?!\s*select)[^(]*?\)/is', '()', $query );
-		 * chars of the query.
-		 */
-		$query = preg_replace( '/\((?!\s*select)[^(]*?\)/is', '()', substr( $query, 0, 1000 ) );
 		// Quickly match most common queries.
 		if ( preg_match( '/^\s*(?:'
 				. 'SELECT.*?\s+FROM'
 				. '|INSERT(?:\s+LOW_PRIORITY|\s+DELAYED|\s+HIGH_PRIORITY)?(?:\s+IGNORE)?(?:\s+INTO)?'
 				. '|REPLACE(?:\s+LOW_PRIORITY|\s+DELAYED)?(?:\s+INTO)?'
 				. '|UPDATE(?:\s+LOW_PRIORITY)?(?:\s+IGNORE)?'
-				. '|DELETE(?:\s+LOW_PRIORITY|\s+QUICK|\s+IGNORE)*(?:\s+FROM)?'
+				. '|DELETE(?:\s+LOW_PRIORITY|\s+QUICK|\s+IGNORE)*(?:.+?FROM)?'
-				. ')\s+((?:[0-9a-zA-Z$_.`]|[\xC2-\xDF][\x80-\xBF])+)/is', $query, $maybe ) ) {
+				. ')\s+((?:[0-9a-zA-Z$_.`-]|[\xC2-\xDF][\x80-\xBF])+)/is', $query, $maybe ) ) {
 			return str_replace( '`', '', $maybe[1] );
 		}
-		// SHOW TABLE STATUS and SHOW TABLES
+		// SHOW TABLE STATUS and SHOW TABLES WHERE Name = 'wp_posts'
-		if ( preg_match( '/^\s*(?:'
+		if ( preg_match( '/^\s*SHOW\s+(?:TABLE\s+STATUS|(?:FULL\s+)?TABLES).+WHERE\s+Name\s*=\s*("|\')((?:[0-9a-zA-Z$_.-]|[\xC2-\xDF][\x80-\xBF])+)\\1/is', $query, $maybe ) ) {
-				. 'SHOW\s+TABLE\s+STATUS.+(?:LIKE\s+|WHERE\s+Name\s*=\s*)'
+			return $maybe[2];
-				. '|SHOW\s+(?:FULL\s+)?TABLES.+(?:LIKE\s+|WHERE\s+Name\s*=\s*)'
+		}
-				. ')\W((?:[0-9a-zA-Z$_.`]|[\xC2-\xDF][\x80-\xBF])+)\W/is', $query, $maybe ) ) {
-			return str_replace( '`', '', $maybe[1] );
+		// SHOW TABLE STATUS LIKE and SHOW TABLES LIKE 'wp\_123\_%'
+		// This quoted LIKE operand seldom holds a full table name.
+		// It is usually a pattern for matching a prefix so we just
+		// strip the trailing % and unescape the _ to get 'wp_123_'
+		// which drop-ins can use for routing these SQL statements.
+		if ( preg_match( '/^\s*SHOW\s+(?:TABLE\s+STATUS|(?:FULL\s+)?TABLES)\s+(?:WHERE\s+Name\s+)?LIKE\s*("|\')((?:[\\\\0-9a-zA-Z$_.-]|[\xC2-\xDF][\x80-\xBF])+)%?\\1/is', $query, $maybe ) ) {
+			return str_replace( '\\_', '_', $maybe[2] );
 		}
 		// Big pattern for the rest of the table-related queries.
 		if ( preg_match( '/^\s*(?:'
 				. '(?:EXPLAIN\s+(?:EXTENDED\s+)?)?SELECT.*?\s+FROM'
 				. '|CREATE(?:\s+\w+)?\s+INDEX.*\s+ON'
 				. '|DROP\s+INDEX.*\s+ON'
 				. '|LOAD\s+DATA.*INFILE.*INTO\s+TABLE'
 				. '|(?:GRANT|REVOKE).*ON\s+TABLE'
 				. '|SHOW\s+(?:.*FROM|.*TABLE)'
-				. ')\s+\(*\s*((?:[0-9a-zA-Z$_.`]|[\xC2-\xDF][\x80-\xBF])+)\s*\)*/is', $query, $maybe ) ) {
+				. ')\s+\(*\s*((?:[0-9a-zA-Z$_.`-]|[\xC2-\xDF][\x80-\xBF])+)\s*\)*/is', $query, $maybe ) ) {
 			return str_replace( '`', '', $maybe[1] );
 		}
 		return false;
 	}
 	/**
 	 * Load the column metadata from the last query.
 	 *
 	 * @since 3.5.0
 	 *
-	 * @access protected
 	 */
 	protected function load_col_info() {
 		if ( $this->col_info )
 			return;
 		if ( $this->use_mysqli ) {
-			for ( $i = 0; $i < @mysqli_num_fields( $this->result ); $i++ ) {
+			$num_fields = mysqli_num_fields( $this->result );
-				$this->col_info[ $i ] = @mysqli_fetch_field( $this->result );
+			for ( $i = 0; $i < $num_fields; $i++ ) {
+				$this->col_info[ $i ] = mysqli_fetch_field( $this->result );
 			}
 		} else {
-			for ( $i = 0; $i < @mysql_num_fields( $this->result ); $i++ ) {
+			$num_fields = mysql_num_fields( $this->result );
-				$this->col_info[ $i ] = @mysql_fetch_field( $this->result, $i );
+			for ( $i = 0; $i < $num_fields; $i++ ) {
+				$this->col_info[ $i ] = mysql_fetch_field( $this->result, $i );
 			}
 		}
 	}
 	/**
 	 * Retrieve column metadata from the last query.
 	 *
 	 * @since 0.71
 	 *
-	 * @param string $info_type Optional. Type one of name, table, def, max_length, not_null, primary_key, multiple_key, unique_key, numeric, blob, type, unsigned, zerofill
+	 * @param string $info_type  Optional. Type one of name, table, def, max_length, not_null, primary_key, multiple_key, unique_key, numeric, blob, type, unsigned, zerofill
-	 * @param int $col_offset Optional. 0: col name. 1: which table the col's in. 2: col's max length. 3: if the col is numeric. 4: col's type
+	 * @param int    $col_offset Optional. 0: col name. 1: which table the col's in. 2: col's max length. 3: if the col is numeric. 4: col's type
 	 * @return mixed Column Results
 	 */
 	public function get_col_info( $info_type = 'name', $col_offset = -1 ) {
 		$this->load_col_info();
 		if ( $this->col_info ) {
 			if ( $col_offset == -1 ) {
 				$i = 0;
 				$new_array = array();
-				foreach( (array) $this->col_info as $col ) {
+				foreach ( (array) $this->col_info as $col ) {
 					$new_array[$i] = $col->{$info_type};
 					$i++;
 				}
 				return $new_array;
 			} else {
 	/**
 	 * Starts the timer, for debugging purposes.
 	 *
 	 * @since 1.5.0
 	 *
-	 * @return bool
+	 * @return true
 	 */
 	public function timer_start() {
 		$this->time_start = microtime( true );
 		return true;
 	}
 	 *
 	 * Will not die if wpdb::$show_errors is false.
 	 *
 	 * @since 1.5.0
 	 *
-	 * @param string $message The Error message
+	 * @param string $message    The Error message
 	 * @param string $error_code Optional. A Computer readable string to identify the error.
 	 * @return false|void
 	 */
 	public function bail( $message, $error_code = '500' ) {
 		if ( !$this->show_errors ) {
-			if ( class_exists( 'WP_Error' ) )
+			if ( class_exists( 'WP_Error', false ) ) {
 				$this->error = new WP_Error($error_code, $message);
-			else
+			} else {
 				$this->error = $message;
+			}
 			return false;
 		}
 		wp_die($message);
 	}
+	/**
+	 * Closes the current database connection.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @return bool True if the connection was successfully closed, false if it wasn't,
+	 *              or the connection doesn't exist.
+	 */
+	public function close() {
+		if ( ! $this->dbh ) {
+			return false;
+		}
+		if ( $this->use_mysqli ) {
+			$closed = mysqli_close( $this->dbh );
+		} else {
+			$closed = mysql_close( $this->dbh );
+		}
+		if ( $closed ) {
+			$this->dbh = null;
+			$this->ready = false;
+			$this->has_connected = false;
+		}
+		return $closed;
+	}
 	/**
 	 * Whether MySQL database is at least the required minimum version.
 	 *
 	 * @since 2.5.0
-	 * @uses $wp_version
+	 *
-	 * @uses $required_mysql_version
+	 * @global string $wp_version
-	 *
+	 * @global string $required_mysql_version
-	 * @return WP_Error
+	 *
+	 * @return WP_Error|void
 	 */
 	public function check_database_version() {
 		global $wp_version, $required_mysql_version;
 		// Make sure the server has the required MySQL version
-		if ( version_compare($this->db_version(), $required_mysql_version, '<') )
+		if ( version_compare($this->db_version(), $required_mysql_version, '<') ) {
+			/* translators: 1: WordPress version number, 2: Minimum required MySQL version number */
 			return new WP_Error('database_version', sprintf( __( '<strong>ERROR</strong>: WordPress %1$s requires MySQL %2$s or higher' ), $wp_version, $required_mysql_version ));
+		}
 	}
 	/**
 	 * Whether the database supports collation.
 	 *
 	 * Called when WordPress is generating the table scheme.
 	 *
+	 * Use `wpdb::has_cap( 'collation' )`.
+	 *
 	 * @since 2.5.0
-	 * @deprecated 3.5.0
+	 * @deprecated 3.5.0 Use wpdb::has_cap()
-	 * @deprecated Use wpdb::has_cap( 'collation' )
 	 *
 	 * @return bool True if collation is supported, false if version does not
 	 */
 	public function supports_collation() {
-		_deprecated_function( __FUNCTION__, '3.5', 'wpdb::has_cap( \'collation\' )' );
+		_deprecated_function( __FUNCTION__, '3.5.0', 'wpdb::has_cap( \'collation\' )' );
 		return $this->has_cap( 'collation' );
 	}
 	/**
 	 * The database character collate.
 	/**
 	 * Determine if a database supports a particular feature.
 	 *
 	 * @since 2.7.0
-	 * @since 4.1.0 Support was added for the 'utf8mb4' feature.
+	 * @since 4.1.0 Added support for the 'utf8mb4' feature.
+	 * @since 4.6.0 Added support for the 'utf8mb4_520' feature.
 	 *
 	 * @see wpdb::db_version()
 	 *
 	 * @param string $db_cap The feature to check for. Accepts 'collation',
 	 *                       'group_concat', 'subqueries', 'set_charset',
-	 *                       or 'utf8mb4'.
+	 *                       'utf8mb4', or 'utf8mb4_520'.
-	 * @return bool Whether the database feature is supported, false otherwise.
+	 * @return int|false Whether the database feature is supported, false otherwise.
 	 */
 	public function has_cap( $db_cap ) {
 		$version = $this->db_version();
 		switch ( strtolower( $db_cap ) ) {
 					$client_version = preg_replace( '/^\D+([\d.]+).*/', '$1', $client_version );
 					return version_compare( $client_version, '5.0.9', '>=' );
 				} else {
 					return version_compare( $client_version, '5.5.3', '>=' );
 				}
+			case 'utf8mb4_520' : // @since 4.6.0
+				return version_compare( $version, '5.6', '>=' );
 		}
 		return false;
 	}
 	 * Searches up the list of functions until it reaches
 	 * the one that would most logically had called this method.
 	 *
 	 * @since 2.5.0
 	 *
-	 * @return string The name of the calling function
+	 * @return string|array The name of the calling function
 	 */
 	public function get_caller() {
 		return wp_debug_backtrace_summary( __CLASS__ );
 	}
 	/**
-	 * The database version number.
+	 * Retrieves the MySQL server version.
 	 *
 	 * @since 2.7.0
 	 *
 	 * @return null|string Null on failure, version number on success.
 	 */

changeset 7	cf61fcea0001
parent 5	5e2f62d02dcd
child 9	177826044cd9