wp/wp-includes/cache.php
changeset 16 a86126ab1dd4
parent 9 177826044cd9
child 18 be944660c56a
equal deleted inserted replaced
15:3d4e9c994f10 16:a86126ab1dd4
     5  * @link https://codex.wordpress.org/Class_Reference/WP_Object_Cache
     5  * @link https://codex.wordpress.org/Class_Reference/WP_Object_Cache
     6  *
     6  *
     7  * @package WordPress
     7  * @package WordPress
     8  * @subpackage Cache
     8  * @subpackage Cache
     9  */
     9  */
       
    10 
       
    11 /** WP_Object_Cache class */
       
    12 require_once ABSPATH . WPINC . '/class-wp-object-cache.php';
    10 
    13 
    11 /**
    14 /**
    12  * Adds data to the cache, if the cache key doesn't already exist.
    15  * Adds data to the cache, if the cache key doesn't already exist.
    13  *
    16  *
    14  * @since 2.0.0
    17  * @since 2.0.0
    20  * @param mixed      $data   The data to add to the cache.
    23  * @param mixed      $data   The data to add to the cache.
    21  * @param string     $group  Optional. The group to add the cache to. Enables the same key
    24  * @param string     $group  Optional. The group to add the cache to. Enables the same key
    22  *                           to be used across groups. Default empty.
    25  *                           to be used across groups. Default empty.
    23  * @param int        $expire Optional. When the cache data should expire, in seconds.
    26  * @param int        $expire Optional. When the cache data should expire, in seconds.
    24  *                           Default 0 (no expiration).
    27  *                           Default 0 (no expiration).
    25  * @return bool False if cache key and group already exist, true on success.
    28  * @return bool True on success, false if cache key and group already exist.
    26  */
    29  */
    27 function wp_cache_add( $key, $data, $group = '', $expire = 0 ) {
    30 function wp_cache_add( $key, $data, $group = '', $expire = 0 ) {
    28 	global $wp_object_cache;
    31 	global $wp_object_cache;
    29 
    32 
    30 	return $wp_object_cache->add( $key, $data, $group, (int) $expire );
    33 	return $wp_object_cache->add( $key, $data, $group, (int) $expire );
    56  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
    59  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
    57  *
    60  *
    58  * @param int|string $key    The cache key to decrement.
    61  * @param int|string $key    The cache key to decrement.
    59  * @param int        $offset Optional. The amount by which to decrement the item's value. Default 1.
    62  * @param int        $offset Optional. The amount by which to decrement the item's value. Default 1.
    60  * @param string     $group  Optional. The group the key is in. Default empty.
    63  * @param string     $group  Optional. The group the key is in. Default empty.
    61  * @return false|int False on failure, the item's new value on success.
    64  * @return int|false The item's new value on success, false on failure.
    62  */
    65  */
    63 function wp_cache_decr( $key, $offset = 1, $group = '' ) {
    66 function wp_cache_decr( $key, $offset = 1, $group = '' ) {
    64 	global $wp_object_cache;
    67 	global $wp_object_cache;
    65 
    68 
    66 	return $wp_object_cache->decr( $key, $offset, $group );
    69 	return $wp_object_cache->decr( $key, $offset, $group );
    90  * @since 2.0.0
    93  * @since 2.0.0
    91  *
    94  *
    92  * @see WP_Object_Cache::flush()
    95  * @see WP_Object_Cache::flush()
    93  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
    96  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
    94  *
    97  *
    95  * @return bool False on failure, true on success
    98  * @return bool True on success, false on failure.
    96  */
    99  */
    97 function wp_cache_flush() {
   100 function wp_cache_flush() {
    98 	global $wp_object_cache;
   101 	global $wp_object_cache;
    99 
   102 
   100 	return $wp_object_cache->flush();
   103 	return $wp_object_cache->flush();
   106  * @since 2.0.0
   109  * @since 2.0.0
   107  *
   110  *
   108  * @see WP_Object_Cache::get()
   111  * @see WP_Object_Cache::get()
   109  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
   112  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
   110  *
   113  *
   111  * @param int|string  $key    The key under which the cache contents are stored.
   114  * @param int|string $key   The key under which the cache contents are stored.
   112  * @param string      $group  Optional. Where the cache contents are grouped. Default empty.
   115  * @param string     $group Optional. Where the cache contents are grouped. Default empty.
   113  * @param bool        $force  Optional. Whether to force an update of the local cache from the persistent
   116  * @param bool       $force Optional. Whether to force an update of the local cache
   114  *                            cache. Default false.
   117  *                          from the persistent cache. Default false.
   115  * @param bool        $found  Optional. Whether the key was found in the cache (passed by reference).
   118  * @param bool       $found Optional. Whether the key was found in the cache (passed by reference).
   116  *                            Disambiguates a return of false, a storable value. Default null.
   119  *                          Disambiguates a return of false, a storable value. Default null.
   117  * @return bool|mixed False on failure to retrieve contents or the cache
   120  * @return mixed|false The cache contents on success, false on failure to retrieve contents.
   118  *                    contents on success
       
   119  */
   121  */
   120 function wp_cache_get( $key, $group = '', $force = false, &$found = null ) {
   122 function wp_cache_get( $key, $group = '', $force = false, &$found = null ) {
   121 	global $wp_object_cache;
   123 	global $wp_object_cache;
   122 
   124 
   123 	return $wp_object_cache->get( $key, $group, $force, $found );
   125 	return $wp_object_cache->get( $key, $group, $force, $found );
       
   126 }
       
   127 
       
   128 /**
       
   129  * Retrieves multiple values from the cache in one call.
       
   130  *
       
   131  * @since 5.5.0
       
   132  *
       
   133  * @see WP_Object_Cache::get_multiple()
       
   134  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
       
   135  *
       
   136  * @param array  $keys  Array of keys under which the cache contents are stored.
       
   137  * @param string $group Optional. Where the cache contents are grouped. Default empty.
       
   138  * @param bool   $force Optional. Whether to force an update of the local cache
       
   139  *                      from the persistent cache. Default false.
       
   140  * @return array Array of values organized into groups.
       
   141  */
       
   142 function wp_cache_get_multiple( $keys, $group = '', $force = false ) {
       
   143 	global $wp_object_cache;
       
   144 
       
   145 	return $wp_object_cache->get_multiple( $keys, $group, $force );
   124 }
   146 }
   125 
   147 
   126 /**
   148 /**
   127  * Increment numeric cache item's value
   149  * Increment numeric cache item's value
   128  *
   150  *
   132  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
   154  * @global WP_Object_Cache $wp_object_cache Object cache global instance.
   133  *
   155  *
   134  * @param int|string $key    The key for the cache contents that should be incremented.
   156  * @param int|string $key    The key for the cache contents that should be incremented.
   135  * @param int        $offset Optional. The amount by which to increment the item's value. Default 1.
   157  * @param int        $offset Optional. The amount by which to increment the item's value. Default 1.
   136  * @param string     $group  Optional. The group the key is in. Default empty.
   158  * @param string     $group  Optional. The group the key is in. Default empty.
   137  * @return false|int False on failure, the item's new value on success.
   159  * @return int|false The item's new value on success, false on failure.
   138  */
   160  */
   139 function wp_cache_incr( $key, $offset = 1, $group = '' ) {
   161 function wp_cache_incr( $key, $offset = 1, $group = '' ) {
   140 	global $wp_object_cache;
   162 	global $wp_object_cache;
   141 
   163 
   142 	return $wp_object_cache->incr( $key, $offset, $group );
   164 	return $wp_object_cache->incr( $key, $offset, $group );
   189  * @param mixed      $data   The contents to store in the cache.
   211  * @param mixed      $data   The contents to store in the cache.
   190  * @param string     $group  Optional. Where to group the cache contents. Enables the same key
   212  * @param string     $group  Optional. Where to group the cache contents. Enables the same key
   191  *                           to be used across groups. Default empty.
   213  *                           to be used across groups. Default empty.
   192  * @param int        $expire Optional. When to expire the cache contents, in seconds.
   214  * @param int        $expire Optional. When to expire the cache contents, in seconds.
   193  *                           Default 0 (no expiration).
   215  *                           Default 0 (no expiration).
   194  * @return bool False on failure, true on success
   216  * @return bool True on success, false on failure.
   195  */
   217  */
   196 function wp_cache_set( $key, $data, $group = '', $expire = 0 ) {
   218 function wp_cache_set( $key, $data, $group = '', $expire = 0 ) {
   197 	global $wp_object_cache;
   219 	global $wp_object_cache;
   198 
   220 
   199 	return $wp_object_cache->set( $key, $data, $group, (int) $expire );
   221 	return $wp_object_cache->set( $key, $data, $group, (int) $expire );
   268 
   290 
   269 	global $wp_object_cache;
   291 	global $wp_object_cache;
   270 
   292 
   271 	$wp_object_cache->reset();
   293 	$wp_object_cache->reset();
   272 }
   294 }
   273 
       
   274 /**
       
   275  * Core class that implements an object cache.
       
   276  *
       
   277  * The WordPress Object Cache is used to save on trips to the database. The
       
   278  * Object Cache stores all of the cache data to memory and makes the cache
       
   279  * contents available by using a key, which is used to name and later retrieve
       
   280  * the cache contents.
       
   281  *
       
   282  * The Object Cache can be replaced by other caching mechanisms by placing files
       
   283  * in the wp-content folder which is looked at in wp-settings. If that file
       
   284  * exists, then this file will not be included.
       
   285  *
       
   286  * @since 2.0.0
       
   287  */
       
   288 class WP_Object_Cache {
       
   289 
       
   290 	/**
       
   291 	 * Holds the cached objects.
       
   292 	 *
       
   293 	 * @since 2.0.0
       
   294 	 * @var array
       
   295 	 */
       
   296 	private $cache = array();
       
   297 
       
   298 	/**
       
   299 	 * The amount of times the cache data was already stored in the cache.
       
   300 	 *
       
   301 	 * @since 2.5.0
       
   302 	 * @var int
       
   303 	 */
       
   304 	public $cache_hits = 0;
       
   305 
       
   306 	/**
       
   307 	 * Amount of times the cache did not have the request in cache.
       
   308 	 *
       
   309 	 * @since 2.0.0
       
   310 	 * @var int
       
   311 	 */
       
   312 	public $cache_misses = 0;
       
   313 
       
   314 	/**
       
   315 	 * List of global cache groups.
       
   316 	 *
       
   317 	 * @since 3.0.0
       
   318 	 * @var array
       
   319 	 */
       
   320 	protected $global_groups = array();
       
   321 
       
   322 	/**
       
   323 	 * The blog prefix to prepend to keys in non-global groups.
       
   324 	 *
       
   325 	 * @since 3.5.0
       
   326 	 * @var string
       
   327 	 */
       
   328 	private $blog_prefix;
       
   329 
       
   330 	/**
       
   331 	 * Holds the value of is_multisite().
       
   332 	 *
       
   333 	 * @since 3.5.0
       
   334 	 * @var bool
       
   335 	 */
       
   336 	private $multisite;
       
   337 
       
   338 	/**
       
   339 	 * Makes private properties readable for backward compatibility.
       
   340 	 *
       
   341 	 * @since 4.0.0
       
   342 	 *
       
   343 	 * @param string $name Property to get.
       
   344 	 * @return mixed Property.
       
   345 	 */
       
   346 	public function __get( $name ) {
       
   347 		return $this->$name;
       
   348 	}
       
   349 
       
   350 	/**
       
   351 	 * Makes private properties settable for backward compatibility.
       
   352 	 *
       
   353 	 * @since 4.0.0
       
   354 	 *
       
   355 	 * @param string $name  Property to set.
       
   356 	 * @param mixed  $value Property value.
       
   357 	 * @return mixed Newly-set property.
       
   358 	 */
       
   359 	public function __set( $name, $value ) {
       
   360 		return $this->$name = $value;
       
   361 	}
       
   362 
       
   363 	/**
       
   364 	 * Makes private properties checkable for backward compatibility.
       
   365 	 *
       
   366 	 * @since 4.0.0
       
   367 	 *
       
   368 	 * @param string $name Property to check if set.
       
   369 	 * @return bool Whether the property is set.
       
   370 	 */
       
   371 	public function __isset( $name ) {
       
   372 		return isset( $this->$name );
       
   373 	}
       
   374 
       
   375 	/**
       
   376 	 * Makes private properties un-settable for backward compatibility.
       
   377 	 *
       
   378 	 * @since 4.0.0
       
   379 	 *
       
   380 	 * @param string $name Property to unset.
       
   381 	 */
       
   382 	public function __unset( $name ) {
       
   383 		unset( $this->$name );
       
   384 	}
       
   385 
       
   386 	/**
       
   387 	 * Adds data to the cache if it doesn't already exist.
       
   388 	 *
       
   389 	 * @since 2.0.0
       
   390 	 *
       
   391 	 * @uses WP_Object_Cache::_exists() Checks to see if the cache already has data.
       
   392 	 * @uses WP_Object_Cache::set()     Sets the data after the checking the cache
       
   393 	 *                                  contents existence.
       
   394 	 *
       
   395 	 * @param int|string $key    What to call the contents in the cache.
       
   396 	 * @param mixed      $data   The contents to store in the cache.
       
   397 	 * @param string     $group  Optional. Where to group the cache contents. Default 'default'.
       
   398 	 * @param int        $expire Optional. When to expire the cache contents. Default 0 (no expiration).
       
   399 	 * @return bool False if cache key and group already exist, true on success
       
   400 	 */
       
   401 	public function add( $key, $data, $group = 'default', $expire = 0 ) {
       
   402 		if ( wp_suspend_cache_addition() ) {
       
   403 			return false;
       
   404 		}
       
   405 
       
   406 		if ( empty( $group ) ) {
       
   407 			$group = 'default';
       
   408 		}
       
   409 
       
   410 		$id = $key;
       
   411 		if ( $this->multisite && ! isset( $this->global_groups[ $group ] ) ) {
       
   412 			$id = $this->blog_prefix . $key;
       
   413 		}
       
   414 
       
   415 		if ( $this->_exists( $id, $group ) ) {
       
   416 			return false;
       
   417 		}
       
   418 
       
   419 		return $this->set( $key, $data, $group, (int) $expire );
       
   420 	}
       
   421 
       
   422 	/**
       
   423 	 * Sets the list of global cache groups.
       
   424 	 *
       
   425 	 * @since 3.0.0
       
   426 	 *
       
   427 	 * @param array $groups List of groups that are global.
       
   428 	 */
       
   429 	public function add_global_groups( $groups ) {
       
   430 		$groups = (array) $groups;
       
   431 
       
   432 		$groups              = array_fill_keys( $groups, true );
       
   433 		$this->global_groups = array_merge( $this->global_groups, $groups );
       
   434 	}
       
   435 
       
   436 	/**
       
   437 	 * Decrements numeric cache item's value.
       
   438 	 *
       
   439 	 * @since 3.3.0
       
   440 	 *
       
   441 	 * @param int|string $key    The cache key to decrement.
       
   442 	 * @param int        $offset Optional. The amount by which to decrement the item's value. Default 1.
       
   443 	 * @param string     $group  Optional. The group the key is in. Default 'default'.
       
   444 	 * @return false|int False on failure, the item's new value on success.
       
   445 	 */
       
   446 	public function decr( $key, $offset = 1, $group = 'default' ) {
       
   447 		if ( empty( $group ) ) {
       
   448 			$group = 'default';
       
   449 		}
       
   450 
       
   451 		if ( $this->multisite && ! isset( $this->global_groups[ $group ] ) ) {
       
   452 			$key = $this->blog_prefix . $key;
       
   453 		}
       
   454 
       
   455 		if ( ! $this->_exists( $key, $group ) ) {
       
   456 			return false;
       
   457 		}
       
   458 
       
   459 		if ( ! is_numeric( $this->cache[ $group ][ $key ] ) ) {
       
   460 			$this->cache[ $group ][ $key ] = 0;
       
   461 		}
       
   462 
       
   463 		$offset = (int) $offset;
       
   464 
       
   465 		$this->cache[ $group ][ $key ] -= $offset;
       
   466 
       
   467 		if ( $this->cache[ $group ][ $key ] < 0 ) {
       
   468 			$this->cache[ $group ][ $key ] = 0;
       
   469 		}
       
   470 
       
   471 		return $this->cache[ $group ][ $key ];
       
   472 	}
       
   473 
       
   474 	/**
       
   475 	 * Removes the contents of the cache key in the group.
       
   476 	 *
       
   477 	 * If the cache key does not exist in the group, then nothing will happen.
       
   478 	 *
       
   479 	 * @since 2.0.0
       
   480 	 *
       
   481 	 * @param int|string $key        What the contents in the cache are called.
       
   482 	 * @param string     $group      Optional. Where the cache contents are grouped. Default 'default'.
       
   483 	 * @param bool       $deprecated Optional. Unused. Default false.
       
   484 	 * @return bool False if the contents weren't deleted and true on success.
       
   485 	 */
       
   486 	public function delete( $key, $group = 'default', $deprecated = false ) {
       
   487 		if ( empty( $group ) ) {
       
   488 			$group = 'default';
       
   489 		}
       
   490 
       
   491 		if ( $this->multisite && ! isset( $this->global_groups[ $group ] ) ) {
       
   492 			$key = $this->blog_prefix . $key;
       
   493 		}
       
   494 
       
   495 		if ( ! $this->_exists( $key, $group ) ) {
       
   496 			return false;
       
   497 		}
       
   498 
       
   499 		unset( $this->cache[ $group ][ $key ] );
       
   500 		return true;
       
   501 	}
       
   502 
       
   503 	/**
       
   504 	 * Clears the object cache of all data.
       
   505 	 *
       
   506 	 * @since 2.0.0
       
   507 	 *
       
   508 	 * @return true Always returns true.
       
   509 	 */
       
   510 	public function flush() {
       
   511 		$this->cache = array();
       
   512 
       
   513 		return true;
       
   514 	}
       
   515 
       
   516 	/**
       
   517 	 * Retrieves the cache contents, if it exists.
       
   518 	 *
       
   519 	 * The contents will be first attempted to be retrieved by searching by the
       
   520 	 * key in the cache group. If the cache is hit (success) then the contents
       
   521 	 * are returned.
       
   522 	 *
       
   523 	 * On failure, the number of cache misses will be incremented.
       
   524 	 *
       
   525 	 * @since 2.0.0
       
   526 	 *
       
   527 	 * @param int|string $key    What the contents in the cache are called.
       
   528 	 * @param string     $group  Optional. Where the cache contents are grouped. Default 'default'.
       
   529 	 * @param bool       $force  Optional. Unused. Whether to force a refetch rather than relying on the local
       
   530 	 *                           cache. Default false.
       
   531 	 * @param bool       $found  Optional. Whether the key was found in the cache (passed by reference).
       
   532 	 *                           Disambiguates a return of false, a storable value. Default null.
       
   533 	 * @return false|mixed False on failure to retrieve contents or the cache contents on success.
       
   534 	 */
       
   535 	public function get( $key, $group = 'default', $force = false, &$found = null ) {
       
   536 		if ( empty( $group ) ) {
       
   537 			$group = 'default';
       
   538 		}
       
   539 
       
   540 		if ( $this->multisite && ! isset( $this->global_groups[ $group ] ) ) {
       
   541 			$key = $this->blog_prefix . $key;
       
   542 		}
       
   543 
       
   544 		if ( $this->_exists( $key, $group ) ) {
       
   545 			$found             = true;
       
   546 			$this->cache_hits += 1;
       
   547 			if ( is_object( $this->cache[ $group ][ $key ] ) ) {
       
   548 				return clone $this->cache[ $group ][ $key ];
       
   549 			} else {
       
   550 				return $this->cache[ $group ][ $key ];
       
   551 			}
       
   552 		}
       
   553 
       
   554 		$found               = false;
       
   555 		$this->cache_misses += 1;
       
   556 		return false;
       
   557 	}
       
   558 
       
   559 	/**
       
   560 	 * Increments numeric cache item's value.
       
   561 	 *
       
   562 	 * @since 3.3.0
       
   563 	 *
       
   564 	 * @param int|string $key    The cache key to increment
       
   565 	 * @param int        $offset Optional. The amount by which to increment the item's value. Default 1.
       
   566 	 * @param string     $group  Optional. The group the key is in. Default 'default'.
       
   567 	 * @return false|int False on failure, the item's new value on success.
       
   568 	 */
       
   569 	public function incr( $key, $offset = 1, $group = 'default' ) {
       
   570 		if ( empty( $group ) ) {
       
   571 			$group = 'default';
       
   572 		}
       
   573 
       
   574 		if ( $this->multisite && ! isset( $this->global_groups[ $group ] ) ) {
       
   575 			$key = $this->blog_prefix . $key;
       
   576 		}
       
   577 
       
   578 		if ( ! $this->_exists( $key, $group ) ) {
       
   579 			return false;
       
   580 		}
       
   581 
       
   582 		if ( ! is_numeric( $this->cache[ $group ][ $key ] ) ) {
       
   583 			$this->cache[ $group ][ $key ] = 0;
       
   584 		}
       
   585 
       
   586 		$offset = (int) $offset;
       
   587 
       
   588 		$this->cache[ $group ][ $key ] += $offset;
       
   589 
       
   590 		if ( $this->cache[ $group ][ $key ] < 0 ) {
       
   591 			$this->cache[ $group ][ $key ] = 0;
       
   592 		}
       
   593 
       
   594 		return $this->cache[ $group ][ $key ];
       
   595 	}
       
   596 
       
   597 	/**
       
   598 	 * Replaces the contents in the cache, if contents already exist.
       
   599 	 *
       
   600 	 * @since 2.0.0
       
   601 	 *
       
   602 	 * @see WP_Object_Cache::set()
       
   603 	 *
       
   604 	 * @param int|string $key    What to call the contents in the cache.
       
   605 	 * @param mixed      $data   The contents to store in the cache.
       
   606 	 * @param string     $group  Optional. Where to group the cache contents. Default 'default'.
       
   607 	 * @param int        $expire Optional. When to expire the cache contents. Default 0 (no expiration).
       
   608 	 * @return bool False if not exists, true if contents were replaced.
       
   609 	 */
       
   610 	public function replace( $key, $data, $group = 'default', $expire = 0 ) {
       
   611 		if ( empty( $group ) ) {
       
   612 			$group = 'default';
       
   613 		}
       
   614 
       
   615 		$id = $key;
       
   616 		if ( $this->multisite && ! isset( $this->global_groups[ $group ] ) ) {
       
   617 			$id = $this->blog_prefix . $key;
       
   618 		}
       
   619 
       
   620 		if ( ! $this->_exists( $id, $group ) ) {
       
   621 			return false;
       
   622 		}
       
   623 
       
   624 		return $this->set( $key, $data, $group, (int) $expire );
       
   625 	}
       
   626 
       
   627 	/**
       
   628 	 * Resets cache keys.
       
   629 	 *
       
   630 	 * @since 3.0.0
       
   631 	 *
       
   632 	 * @deprecated 3.5.0 Use switch_to_blog()
       
   633 	 * @see switch_to_blog()
       
   634 	 */
       
   635 	public function reset() {
       
   636 		_deprecated_function( __FUNCTION__, '3.5.0', 'switch_to_blog()' );
       
   637 
       
   638 		// Clear out non-global caches since the blog ID has changed.
       
   639 		foreach ( array_keys( $this->cache ) as $group ) {
       
   640 			if ( ! isset( $this->global_groups[ $group ] ) ) {
       
   641 				unset( $this->cache[ $group ] );
       
   642 			}
       
   643 		}
       
   644 	}
       
   645 
       
   646 	/**
       
   647 	 * Sets the data contents into the cache.
       
   648 	 *
       
   649 	 * The cache contents are grouped by the $group parameter followed by the
       
   650 	 * $key. This allows for duplicate ids in unique groups. Therefore, naming of
       
   651 	 * the group should be used with care and should follow normal function
       
   652 	 * naming guidelines outside of core WordPress usage.
       
   653 	 *
       
   654 	 * The $expire parameter is not used, because the cache will automatically
       
   655 	 * expire for each time a page is accessed and PHP finishes. The method is
       
   656 	 * more for cache plugins which use files.
       
   657 	 *
       
   658 	 * @since 2.0.0
       
   659 	 *
       
   660 	 * @param int|string $key    What to call the contents in the cache.
       
   661 	 * @param mixed      $data   The contents to store in the cache.
       
   662 	 * @param string     $group  Optional. Where to group the cache contents. Default 'default'.
       
   663 	 * @param int        $expire Not Used.
       
   664 	 * @return true Always returns true.
       
   665 	 */
       
   666 	public function set( $key, $data, $group = 'default', $expire = 0 ) {
       
   667 		if ( empty( $group ) ) {
       
   668 			$group = 'default';
       
   669 		}
       
   670 
       
   671 		if ( $this->multisite && ! isset( $this->global_groups[ $group ] ) ) {
       
   672 			$key = $this->blog_prefix . $key;
       
   673 		}
       
   674 
       
   675 		if ( is_object( $data ) ) {
       
   676 			$data = clone $data;
       
   677 		}
       
   678 
       
   679 		$this->cache[ $group ][ $key ] = $data;
       
   680 		return true;
       
   681 	}
       
   682 
       
   683 	/**
       
   684 	 * Echoes the stats of the caching.
       
   685 	 *
       
   686 	 * Gives the cache hits, and cache misses. Also prints every cached group,
       
   687 	 * key and the data.
       
   688 	 *
       
   689 	 * @since 2.0.0
       
   690 	 */
       
   691 	public function stats() {
       
   692 		echo '<p>';
       
   693 		echo "<strong>Cache Hits:</strong> {$this->cache_hits}<br />";
       
   694 		echo "<strong>Cache Misses:</strong> {$this->cache_misses}<br />";
       
   695 		echo '</p>';
       
   696 		echo '<ul>';
       
   697 		foreach ( $this->cache as $group => $cache ) {
       
   698 			echo "<li><strong>Group:</strong> $group - ( " . number_format( strlen( serialize( $cache ) ) / KB_IN_BYTES, 2 ) . 'k )</li>';
       
   699 		}
       
   700 		echo '</ul>';
       
   701 	}
       
   702 
       
   703 	/**
       
   704 	 * Switches the internal blog ID.
       
   705 	 *
       
   706 	 * This changes the blog ID used to create keys in blog specific groups.
       
   707 	 *
       
   708 	 * @since 3.5.0
       
   709 	 *
       
   710 	 * @param int $blog_id Blog ID.
       
   711 	 */
       
   712 	public function switch_to_blog( $blog_id ) {
       
   713 		$blog_id           = (int) $blog_id;
       
   714 		$this->blog_prefix = $this->multisite ? $blog_id . ':' : '';
       
   715 	}
       
   716 
       
   717 	/**
       
   718 	 * Serves as a utility function to determine whether a key exists in the cache.
       
   719 	 *
       
   720 	 * @since 3.4.0
       
   721 	 *
       
   722 	 * @param int|string $key   Cache key to check for existence.
       
   723 	 * @param string     $group Cache group for the key existence check.
       
   724 	 * @return bool Whether the key exists in the cache for the given group.
       
   725 	 */
       
   726 	protected function _exists( $key, $group ) {
       
   727 		return isset( $this->cache[ $group ] ) && ( isset( $this->cache[ $group ][ $key ] ) || array_key_exists( $key, $this->cache[ $group ] ) );
       
   728 	}
       
   729 
       
   730 	/**
       
   731 	 * Sets up object properties; PHP 5 style constructor.
       
   732 	 *
       
   733 	 * @since 2.0.8
       
   734 	 */
       
   735 	public function __construct() {
       
   736 		$this->multisite   = is_multisite();
       
   737 		$this->blog_prefix = $this->multisite ? get_current_blog_id() . ':' : '';
       
   738 
       
   739 		/**
       
   740 		 * @todo This should be moved to the PHP4 style constructor, PHP5
       
   741 		 * already calls __destruct()
       
   742 		 */
       
   743 		register_shutdown_function( array( $this, '__destruct' ) );
       
   744 	}
       
   745 
       
   746 	/**
       
   747 	 * Saves the object cache before object is completely destroyed.
       
   748 	 *
       
   749 	 * Called upon object destruction, which should be when PHP ends.
       
   750 	 *
       
   751 	 * @since 2.0.8
       
   752 	 *
       
   753 	 * @return true Always returns true.
       
   754 	 */
       
   755 	public function __destruct() {
       
   756 		return true;
       
   757 	}
       
   758 }