diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/class-wp-matchesmapregex.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-wp-matchesmapregex.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,91 @@
+<?php
+/**
+ * WP_MatchesMapRegex helper class
+ *
+ * @package WordPress
+ * @since 4.7.0
+ */
+
+/**
+ * Helper class to remove the need to use eval to replace $matches[] in query strings.
+ *
+ * @since 2.9.0
+ */
+class WP_MatchesMapRegex {
+	/**
+	 * store for matches
+	 *
+	 * @var array
+	 */
+	private $_matches;
+
+	/**
+	 * store for mapping result
+	 *
+	 * @var string
+	 */
+	public $output;
+
+	/**
+	 * subject to perform mapping on (query string containing $matches[] references
+	 *
+	 * @var string
+	 */
+	private $_subject;
+
+	/**
+	 * regexp pattern to match $matches[] references
+	 *
+	 * @var string
+	 */
+	public $_pattern = '(\$matches\[[1-9]+[0-9]*\])'; // magic number
+
+	/**
+	 * constructor
+	 *
+	 * @param string $subject subject if regex
+	 * @param array  $matches data to use in map
+	 */
+	public function __construct($subject, $matches) {
+		$this->_subject = $subject;
+		$this->_matches = $matches;
+		$this->output = $this->_map();
+	}
+
+	/**
+	 * Substitute substring matches in subject.
+	 *
+	 * static helper function to ease use
+	 *
+	 * @static
+	 *
+	 * @param string $subject subject
+	 * @param array  $matches data used for substitution
+	 * @return string
+	 */
+	public static function apply($subject, $matches) {
+		$oSelf = new WP_MatchesMapRegex($subject, $matches);
+		return $oSelf->output;
+	}
+
+	/**
+	 * do the actual mapping
+	 *
+	 * @return string
+	 */
+	private function _map() {
+		$callback = array($this, 'callback');
+		return preg_replace_callback($this->_pattern, $callback, $this->_subject);
+	}
+
+	/**
+	 * preg_replace_callback hook
+	 *
+	 * @param  array $matches preg_replace regexp matches
+	 * @return string
+	 */
+	public function callback($matches) {
+		$index = intval(substr($matches[0], 9, -1));
+		return ( isset( $this->_matches[$index] ) ? urlencode($this->_matches[$index]) : '' );
+	}
+}