+/**
+ * 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
+ *
+ * @access private
+ * @var array
+ */
+ var $_matches;
+
+ /**
+ * store for mapping result
+ *
+ * @access public
+ * @var string
+ */
+ var $output;
+
+ /**
+ * subject to perform mapping on (query string containing $matches[] references
+ *
+ * @access private
+ * @var string
+ */
+ var $_subject;
+
+ /**
+ * regexp pattern to match $matches[] references
+ *
+ * @var string
+ */
+ var $_pattern = '(\$matches\[[1-9]+[0-9]*\])'; // magic number
+
+ /**
+ * constructor
+ *
+ * @param string $subject subject if regex
+ * @param array $matches data to use in map
+ * @return self
+ */
+ function WP_MatchesMapRegex($subject, $matches) {
+ $this->_subject = $subject;
+ $this->_matches = $matches;
+ $this->output = $this->_map();
+ }
+
+ /**
+ * Substitute substring matches in subject.
+ *
+ * static helper function to ease use
+ *
+ * @access public
+ * @param string $subject subject
+ * @param array $matches data used for subsitution
+ * @return string
+ */
+ function apply($subject, $matches) {
+ $oSelf =& new WP_MatchesMapRegex($subject, $matches);
+ return $oSelf->output;
+ }
+
+ /**
+ * do the actual mapping
+ *
+ * @access private
+ * @return string
+ */
+ function _map() {
+ $callback = array(&$this, 'callback');
+ return preg_replace_callback($this->_pattern, $callback, $this->_subject);
+ }
+
+ /**
+ * preg_replace_callback hook
+ *
+ * @access public
+ * @param array $matches preg_replace regexp matches
+ * @return string
+ */
+ function callback($matches) {
+ $index = intval(substr($matches[0], 9, -1));
+ return ( isset( $this->_matches[$index] ) ? urlencode($this->_matches[$index]) : '' );
+ }
+
+}
+