Changes from branches/3.0/wp-includes/functions.php at r15995 to trunk/wp-includes/functions.php at r17435

File:

• trunk/wp-includes/functions.php (modified) (38 diffs)

trunk/wp-includes/functions.php

@@ -28 +28 @@
         return false;
 
-    if ( 'G' == $dateformatstring ) {
+    if ( 'G' == $dateformatstring )
         return strtotime( $m . ' +0000' );
-    }
 
     $i = strtotime( $m );
@@ -37 +36 @@
         return $i;
 
-    if ( $translate)
-        return date_i18n( $dateformatstring, $i );
+    if ( $translate )
+        return date_i18n( $dateformatstring, $i );
     else
-        return date( $dateformatstring, $i );
+        return date( $dateformatstring, $i );
 }
 
@@ -120 +119 @@
         $dateformatstring = substr( $dateformatstring, 1, strlen( $dateformatstring ) -1 );
     }
+    $timezone_formats = array( 'P', 'I', 'O', 'T', 'Z', 'e' );
+    $timezone_formats_re = implode( '|', $timezone_formats );
+    if ( preg_match( "/$timezone_formats_re/", $dateformatstring ) && wp_timezone_supported() ) {
+        $timezone_string = get_option( 'timezone_string' );
+        if ( $timezone_string ) {
+            $timezone_object = timezone_open( $timezone_string );
+            $date_object = date_create( null, $timezone_object );
+            foreach( $timezone_formats as $timezone_format ) {
+                if ( false !== strpos( $dateformatstring, $timezone_format ) ) {
+                    $formatted = date_format( $date_object, $timezone_format );
+                    $dateformatstring = ' '.$dateformatstring;
+                    $dateformatstring = preg_replace( "/([^\\\])$timezone_format/", "\\1" . backslashit( $formatted ), $dateformatstring );
+                    $dateformatstring = substr( $dateformatstring, 1, strlen( $dateformatstring ) -1 );
+                }
+            }
+        }
+    }
     $j = @$datefunc( $dateformatstring, $i );
     // allow plugins to redo this entirely for languages with untypical grammars
@@ -231 +247 @@
 function is_serialized( $data ) {
     // if it isn't a string, it isn't serialized
-    if ( !is_string( $data ) )
+    if ( ! is_string( $data ) )
         return false;
     $data = trim( $data );
-    if ( 'N;' == $data )
+    if ( 'N;' == $data )
         return true;
-    if ( !preg_match( '/^([adObis]):/', $data, $badions ) )
+    $length = strlen( $data );
+    if ( $length < 4 )
         return false;
-    switch ( $badions[1] ) {
+    if ( ':' !== $data[1] )
+        return false;
+    $lastc = $data[$length-1];
+    if ( ';' !== $lastc && '}' !== $lastc )
+        return false;
+    $token = $data[0];
+    switch ( $token ) {
+        case 's' :
+            if ( '"' !== $data[$length-2] )
+                return false;
         case 'a' :
         case 'O' :
-        case 's' :
-            if ( preg_match( "/^{$badions[1]}:[0-9]+:.*[;}]\$/s", $data ) )
-                return true;
-            break;
+            return (bool) preg_match( "/^{$token}:[0-9]+:/s", $data );
         case 'b' :
         case 'i' :
         case 'd' :
-            if ( preg_match( "/^{$badions[1]}:[0-9.E-]+;\$/", $data ) )
-                return true;
-            break;
+            return (bool) preg_match( "/^{$token}:[0-9.E-]+;\$/", $data );
     }
     return false;
@@ -413 +434 @@
         $wpdb->suppress_errors($suppress);
         $alloptions = array();
-        foreach ( (array) $alloptions_db as $o )
+        foreach ( (array) $alloptions_db as $o ) {
             $alloptions[$o->option_name] = $o->option_value;
-            if ( !defined( 'WP_INSTALLING' ) || !is_multisite() )
-                wp_cache_add( 'alloptions', $alloptions, 'options' );
+        }
+        if ( !defined( 'WP_INSTALLING' ) || !is_multisite() )
+            wp_cache_add( 'alloptions', $alloptions, 'options' );
     }
 
@@ -440 +462 @@
         $site_id = $wpdb->siteid;
 
-    $core_options = array('site_name', 'siteurl', 'active_sitewide_plugins', '_site_transient_timeout_theme_roots', '_site_transient_theme_roots', 'site_admins', 'dashboard_blog', 'can_compress_scripts', 'global_terms_enabled' );
+    $core_options = array('site_name', 'siteurl', 'active_sitewide_plugins', '_site_transient_timeout_theme_roots', '_site_transient_theme_roots', 'site_admins', 'can_compress_scripts', 'global_terms_enabled' );
 
     $core_options_in = "'" . implode("', '", $core_options) . "'";
@@ -547 +569 @@
  * @subpackage Option
  * @since 1.0.0
- * @link http://alex.vort-x.net/blog/ Thanks Alex Stapleton
  *
  * @uses do_action() Calls 'add_option' hook before adding the option.
@@ -671 +692 @@
     global $_wp_using_ext_object_cache;
 
-    do_action( 'delete_transient_' . $transient, $transient );
+    do_action( 'delete_transient_' . $transient, $transient );
 
     if ( $_wp_using_ext_object_cache ) {
@@ -759 +780 @@
     global $_wp_using_ext_object_cache;
 
-    $value = apply_filters( 'pre_set_transient_' . $transient, $value );
+    $value = apply_filters( 'pre_set_transient_' . $transient, $value );
 
     if ( $_wp_using_ext_object_cache ) {
@@ -1164 +1185 @@
 function do_enclose( $content, $post_ID ) {
     global $wpdb;
+
+    //TODO: Tidy this ghetto code up and make the debug code optional
     include_once( ABSPATH . WPINC . '/class-IXR.php' );
 
@@ -1184 +1207 @@
     foreach ( $pung as $link_test ) {
         if ( !in_array( $link_test, $post_links_temp[0] ) ) { // link no longer in post
-            $mid = $wpdb->get_col( $wpdb->prepare("SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE (%s)", $post_ID, $link_test . '%') );
+            $mid = $wpdb->get_col( $wpdb->prepare("SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE (%s)", $post_ID, like_escape( $link_test ) . '%') );
             do_action( 'delete_postmeta', $mid );
             $wpdb->query( $wpdb->prepare("DELETE FROM $wpdb->postmeta WHERE meta_id IN(%s)", implode( ',', $mid ) ) );
@@ -1198 +1221 @@
             if ( isset( $test['query'] ) )
                 $post_links[] = $link_test;
-            elseif ( $test['path'] != '/' && $test['path'] != '' )
+            elseif ( isset($test['path']) && ( $test['path'] != '/' ) &&  ($test['path'] != '' ) )
                 $post_links[] = $link_test;
         }
@@ -1204 +1227 @@
 
     foreach ( (array) $post_links as $url ) {
-        if ( $url != '' && !$wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE (%s)", $post_ID, $url . '%' ) ) ) {
+        if ( $url != '' && !$wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE (%s)", $post_ID, like_escape( $url ) . '%' ) ) ) {
 
             if ( $headers = wp_get_http_headers( $url) ) {
@@ -1322 +1345 @@
  */
 function is_new_day() {
-    global $day, $previousday;
-    if ( $day != $previousday )
+    global $currentday, $previousday;
+    if ( $currentday != $previousday )
         return 1;
     else
@@ -1620 +1643 @@
  * by different browsers
  *
- * @since 2.8
+ * @since 2.8.0
  *
  * @uses apply_filters()
@@ -1634 +1657 @@
 
     if ( function_exists('apply_filters') ) {
-        $headers = apply_filters('nocache_headers', $headers);
+        $headers = (array) apply_filters('nocache_headers', $headers);
     }
     return $headers;
@@ -1650 +1673 @@
 function nocache_headers() {
     $headers = wp_get_nocache_headers();
-    foreach( (array) $headers as $name => $field_value )
+    foreach( $headers as $name => $field_value )
         @header("{$name}: {$field_value}");
 }
@@ -2059 +2082 @@
         return true;
 
-    if ( strlen($path) == 0 || $path{0} == '.' )
+    if ( strlen($path) == 0 || $path[0] == '.' )
         return false;
 
@@ -2191 +2214 @@
  * unique.
  *
- * The callback must accept two parameters, the first one is the directory and
- * the second is the filename. The callback must be a function.
- *
- * @since 2.5
+ * The callback is passed three parameters, the first one is the directory, the
+ * second is the filename, and the third is the extension.
+ *
+ * @since 2.5.0
  *
  * @param string $dir
  * @param string $filename
- * @param string $unique_filename_callback Function name, must be a function.
+ * @param mixed $unique_filename_callback Callback.
  * @return string New filename, if given wasn't unique.
  */
@@ -2214 +2237 @@
         $name = '';
 
-    // Increment the file number until we have a unique file to save in $dir. Use $override['unique_filename_callback'] if supplied.
+    // Increment the file number until we have a unique file to save in $dir. Use callback if supplied.
     if ( $unique_filename_callback && is_callable( $unique_filename_callback ) ) {
-        $filename = $unique_filename_callback( $dir, $name );
+        $filename = call_user_func( $unique_filename_callback, $dir, $name, $ext );
     } else {
         $number = '';
@@ -2574 +2597 @@
         $trans['activate']['plugin']   = array( __( 'Your attempt to activate this plugin: &#8220;%s&#8221; has failed.' ), 'use_id' );
         $trans['deactivate']['plugin'] = array( __( 'Your attempt to deactivate this plugin: &#8220;%s&#8221; has failed.' ), 'use_id' );
-        $trans['upgrade']['plugin']    = array( __( 'Your attempt to upgrade this plugin: &#8220;%s&#8221; has failed.' ), 'use_id' );
+        $trans['upgrade']['plugin']    = array( __( 'Your attempt to update this plugin: &#8220;%s&#8221; has failed.' ), 'use_id' );
 
         $trans['add']['post']          = array( __( 'Your attempt to add this post has failed.' ), false );
@@ -2658 +2681 @@
  */
 function wp_die( $message, $title = '', $args = array() ) {
+    if ( defined( 'DOING_AJAX' ) && DOING_AJAX )
+        die('-1');
+
     if ( function_exists( 'apply_filters' ) ) {
         $function = apply_filters( 'wp_die_handler', '_default_wp_die_handler');
-    }else {
+    } else {
         $function = '_default_wp_die_handler';
     }
@@ -2740 +2766 @@
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <!-- Ticket #11289, IE bug fix: always pad the error page with enough characters such that it is greater than 512 bytes, even after gzip compression abcdefghijklmnopqrstuvwxyz1234567890aabbccddeeffgghhiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz11223344556677889900abacbcbdcdcededfefegfgfhghgihihjijikjkjlklkmlmlnmnmononpopoqpqprqrqsrsrtstsubcbcdcdedefefgfabcadefbghicjkldmnoepqrfstugvwxhyz1i234j567k890laabmbccnddeoeffpgghqhiirjjksklltmmnunoovppqwqrrxsstytuuzvvw0wxx1yyz2z113223434455666777889890091abc2def3ghi4jkl5mno6pqr7stu8vwx9yz11aab2bcc3dd4ee5ff6gg7hh8ii9j0jk1kl2lmm3nnoo4p5pq6qrr7ss8tt9uuvv0wwx1x2yyzz13aba4cbcb5dcdc6dedfef8egf9gfh0ghg1ihi2hji3jik4jkj5lkl6kml7mln8mnm9ono -->
-<html xmlns="http://www.w3.org/1999/xhtml" <?php if ( function_exists( 'language_attributes' ) ) language_attributes(); ?>>
+<html xmlns="http://www.w3.org/1999/xhtml" <?php if ( function_exists( 'language_attributes' ) && function_exists( 'is_rtl' ) ) language_attributes(); else echo "dir='$text_direction'"; ?>>
 <head>
     <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
@@ -2979 +3005 @@
 
 /**
+ * Extract a slice of an array, given a list of keys
+ *
+ * @since 3.1.0
+ *
+ * @param array $array The original array
+ * @param array $keys The list of keys
+ * @return array The array slice
+ */
+function wp_array_slice_assoc( $array, $keys ) {
+    $slice = array();
+    foreach ( $keys as $key )
+        if ( isset( $array[ $key ] ) )
+            $slice[ $key ] = $array[ $key ];
+
+    return $slice;
+}
+
+/**
  * Filters a list of objects, based on a set of key => value arguments
  *
@@ -2991 +3035 @@
  */
 function wp_filter_object_list( $list, $args = array(), $operator = 'and', $field = false ) {
-    if ( !is_array($list) )
+    if ( ! is_array( $list ) )
         return array();
 
-    if ( empty($args) )
-        $args = array();
-
-    if ( empty($args) && !$field )
-        return $list;   // nothing to do
-
-    $count = count($args);
-
+    $list = wp_list_filter( $list, $args, $operator );
+
+    if ( $field )
+        $list = wp_list_pluck( $list, $field );
+
+    return $list;
+}
+
+/**
+ * Filters a list of objects, based on a set of key => value arguments
+ *
+ * @since 3.1.0
+ *
+ * @param array $list An array of objects to filter
+ * @param array $args An array of key => value arguments to match against each object
+ * @param string $operator The logical operation to perform:
+ *    'AND' means all elements from the array must match;
+ *    'OR' means only one element needs to match;
+ *    'NOT' means no elements may match.
+ *   The default is 'AND'.
+ * @return array
+ */
+function wp_list_filter( $list, $args = array(), $operator = 'AND' ) {
+    if ( ! is_array( $list ) )
+        return array();
+
+    if ( empty( $args ) )
+        return $list;
+
+    $operator = strtoupper( $operator );
+    $count = count( $args );
     $filtered = array();
 
     foreach ( $list as $key => $obj ) {
-        $matched = count(array_intersect_assoc(get_object_vars($obj), $args));
-        if ( ('and' == $operator && $matched == $count) || ('or' == $operator && $matched <= $count) ) {
-            if ( $field )
-                $filtered[] = $obj->$field;
-            else
-                $filtered[$key] = $obj;
+        $matched = count( array_intersect_assoc( (array) $obj, $args ) );
+        if ( ( 'AND' == $operator && $matched == $count )
+          || ( 'OR' == $operator && $matched <= $count )
+          || ( 'NOT' == $operator && 0 == $matched ) ) {
+            $filtered[$key] = $obj;
         }
     }
 
     return $filtered;
+}
+
+/**
+ * Pluck a certain field out of each object in a list
+ *
+ * @since 3.1.0
+ *
+ * @param array $list A list of objects or arrays
+ * @param int|string $field A field from the object to place instead of the entire object
+ * @return array
+ */
+function wp_list_pluck( $list, $field ) {
+    foreach ( $list as $key => $value ) {
+        $value = (array) $value;
+        $list[ $key ] = $value[ $field ];
+    }
+
+    return $list;
 }
 
@@ -3070 +3154 @@
     for ($i=0; $i<$levels; $i++)
         ob_end_flush();
-}
-
-/**
- * Load the correct database class file.
- *
- * This function is used to load the database class file either at runtime or by
- * wp-admin/setup-config.php We must globalise $wpdb to ensure that it is
- * defined globally by the inline code in wp-db.php.
- *
- * @since 2.5.0
- * @global $wpdb WordPress Database Object
- */
-function require_wp_db() {
-    global $wpdb;
-    if ( file_exists( WP_CONTENT_DIR . '/db.php' ) )
-        require_once( WP_CONTENT_DIR . '/db.php' );
-    else
-        require_once( ABSPATH . WPINC . '/wp-db.php' );
 }
 
@@ -3210 +3276 @@
  * function.
  *
- * The current behavior is to trigger an user error if WP_DEBUG is true.
- *
- * This function is to be used in every function in depreceated.php
+ * The current behavior is to trigger a user error if WP_DEBUG is true.
+ *
+ * This function is to be used in every function that is deprecated.
  *
  * @package WordPress
@@ -3248 +3314 @@
  * file.
  *
- * The current behavior is to trigger an user error if WP_DEBUG is true.
- *
- * This function is to be used in every file that is depreceated
+ * The current behavior is to trigger a user error if WP_DEBUG is true.
+ *
+ * This function is to be used in every file that is deprecated.
  *
  * @package WordPress
@@ -3296 +3362 @@
  * argument.
  *
- * The current behavior is to trigger an user error if WP_DEBUG is true.
+ * The current behavior is to trigger a user error if WP_DEBUG is true.
  *
  * @package WordPress
@@ -3322 +3388 @@
         else
             trigger_error( sprintf( __('%1$s was called with an argument that is <strong>deprecated</strong> since version %2$s with no alternative available.'), $function, $version ) );
+    }
+}
+
+/**
+ * Marks something as being incorrectly called.
+ *
+ * There is a hook doing_it_wrong_run that will be called that can be used
+ * to get the backtrace up to what file and function called the deprecated
+ * function.
+ *
+ * The current behavior is to trigger a user error if WP_DEBUG is true.
+ *
+ * @package WordPress
+ * @subpackage Debug
+ * @since 3.1.0
+ * @access private
+ *
+ * @uses do_action() Calls 'doing_it_wrong_run' and passes the function arguments.
+ * @uses apply_filters() Calls 'doing_it_wrong_trigger_error' and expects boolean value of true to do
+ *   trigger or false to not trigger error.
+ *
+ * @param string $function The function that was called.
+ * @param string $message A message explaining what has been done incorrectly.
+ * @param string $version The version of WordPress where the message was added.
+ */
+function _doing_it_wrong( $function, $message, $version ) {
+
+    do_action( 'doing_it_wrong_run', $function, $message, $version );
+
+    // Allow plugin to filter the output error trigger
+    if ( WP_DEBUG && apply_filters( 'doing_it_wrong_trigger_error', true ) ) {
+        $version = is_null( $version ) ? '' : sprintf( __( '(This message was added in version %s.)' ), $version );
+        trigger_error( sprintf( __( '%1$s was called <strong>incorrectly</strong>. %2$s %3$s' ), $function, $message, $version ) );
     }
 }
@@ -3368 +3467 @@
 
 /**
+ * Check if IIS 7 supports pretty permalinks
+ *
+ * @since 2.8.0
+ *
+ * @return bool
+ */
+function iis7_supports_permalinks() {
+    global $is_iis7;
+
+    $supports_permalinks = false;
+    if ( $is_iis7 ) {
+        /* First we check if the DOMDocument class exists. If it does not exist,
+         * which is the case for PHP 4.X, then we cannot easily update the xml configuration file,
+         * hence we just bail out and tell user that pretty permalinks cannot be used.
+         * This is not a big issue because PHP 4.X is going to be depricated and for IIS it
+         * is recommended to use PHP 5.X NTS.
+         * Next we check if the URL Rewrite Module 1.1 is loaded and enabled for the web site. When
+         * URL Rewrite 1.1 is loaded it always sets a server variable called 'IIS_UrlRewriteModule'.
+         * Lastly we make sure that PHP is running via FastCGI. This is important because if it runs
+         * via ISAPI then pretty permalinks will not work.
+         */
+        $supports_permalinks = class_exists('DOMDocument') && isset($_SERVER['IIS_UrlRewriteModule']) && ( php_sapi_name() == 'cgi-fcgi' );
+    }
+
+    return apply_filters('iis7_supports_permalinks', $supports_permalinks);
+}
+
+/**
  * File validates against allowed set of defined rules.
  *
@@ -3473 +3600 @@
         $url = preg_replace('|/wp-admin/.*|i', '', $schema . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);
     }
-    return $url;
+    return rtrim($url, '/');
 }
 
@@ -3786 +3913 @@
     global $_wp_using_ext_object_cache;
 
-    $value = apply_filters( 'pre_set_site_transient_' . $transient, $value );
+    $value = apply_filters( 'pre_set_site_transient_' . $transient, $value );
 
     if ( $_wp_using_ext_object_cache ) {
@@ -4137 +4264 @@
 
 /**
- * Parse the file contents to retrieve its metadata.
- *
- * Searches for metadata for a file, such as a plugin or theme.  Each piece of
- * metadata must be on its own line. For a field spanning multple lines, it
- * must not have any newlines or only parts of it will be displayed.
- *
- * Some users have issues with opening large files and manipulating the contents
- * for want is usually the first 1kiB or 2kiB. This function stops pulling in
- * the file contents when it has all of the required data.
- *
- * The first 8kiB of the file will be pulled in and if the file data is not
- * within that first 8kiB, then the author should correct their plugin file
- * and move the data headers to the top.
- *
- * The file is assumed to have permissions to allow for scripts to read
- * the file. This is not checked however and the file is only opened for
- * reading.
+ * Retrieve metadata from a file.
+ *
+ * Searches for metadata in the first 8kiB of a file, such as a plugin or theme.
+ * Each piece of metadata must be on its own line. Fields can not span multple
+ * lines, the value will get cut at the end of the first line.
+ *
+ * If the file data is not within that first 8kiB, then the author should correct
+ * their plugin file and move the data headers to the top.
+ *
+ * @see http://codex.wordpress.org/File_Header
  *
  * @since 2.9.0
- *
  * @param string $file Path to the file
- * @param bool $markup If the returned data should have HTML markup applied
- * @param string $context If specified adds filter hook "extra_<$context>_headers"
+ * @param array $default_headers List of headers, in the format array('HeaderKey' => 'Header Name')
+ * @param string $context If specified adds filter hook "extra_{$context}_headers"
  */
 function get_file_data( $file, $default_headers, $context = '' ) {
@@ -4172 +4291 @@
 
     if ( $context != '' ) {
-        $extra_headers = apply_filters( "extra_$context".'_headers', array() );
+        $extra_headers = apply_filters( "extra_{$context}_headers", array() );
 
         $extra_headers = array_flip( $extra_headers );
@@ -4178 +4297 @@
             $extra_headers[$key] = $key;
         }
-        $all_headers = array_merge($extra_headers, $default_headers);
+        $all_headers = array_merge( $extra_headers, (array) $default_headers );
     } else {
         $all_headers = $default_headers;
     }
 
-
     foreach ( $all_headers as $field => $regex ) {
-        preg_match( '/' . preg_quote( $regex, '/' ) . ':(.*)$/mi', $file_data, ${$field});
+        preg_match( '/^[ \t\/*#]*' . preg_quote( $regex, '/' ) . ':(.*)$/mi', $file_data, ${$field});
         if ( !empty( ${$field} ) )
             ${$field} = _cleanup_header_comment( ${$field}[1] );
@@ -4196 +4314 @@
     return $file_data;
 }
-/*
+
+/**
  * Used internally to tidy up the search terms
  *
@@ -4298 +4417 @@
 }
 
+/**
+ * Finds hierarchy loops using a callback function that maps object IDs to parent IDs.
+ *
+ * @since 3.1.0
+ * @access private
+ *
+ * @param callback $callback function that accepts ( ID, $callback_args ) and outputs parent_ID
+ * @param int $start The ID to start the loop check at
+ * @param int $start_parent the parent_ID of $start to use instead of calling $callback( $start ). Use null to always use $callback
+ * @param array $callback_args optional additional arguments to send to $callback
+ * @return array IDs of all members of loop
+ */
+function wp_find_hierarchy_loop( $callback, $start, $start_parent, $callback_args = array() ) {
+    $override = is_null( $start_parent ) ? array() : array( $start => $start_parent );
+
+    if ( !$arbitrary_loop_member = wp_find_hierarchy_loop_tortoise_hare( $callback, $start, $override, $callback_args ) )
+        return array();
+
+    return wp_find_hierarchy_loop_tortoise_hare( $callback, $arbitrary_loop_member, $override, $callback_args, true );
+}
+
+/**
+ * Uses the "The Tortoise and the Hare" algorithm to detect loops.
+ *
+ * For every step of the algorithm, the hare takes two steps and the tortoise one.
+ * If the hare ever laps the tortoise, there must be a loop.
+ *
+ * @since 3.1.0
+ * @access private
+ *
+ * @param callback $callback function that accupts ( ID, callback_arg, ... ) and outputs parent_ID
+ * @param int $start The ID to start the loop check at
+ * @param array $override an array of ( ID => parent_ID, ... ) to use instead of $callback
+ * @param array $callback_args optional additional arguments to send to $callback
+ * @param bool $_return_loop Return loop members or just detect presence of loop?
+ *             Only set to true if you already know the given $start is part of a loop
+ *             (otherwise the returned array might include branches)
+ * @return mixed scalar ID of some arbitrary member of the loop, or array of IDs of all members of loop if $_return_loop
+ */
+function wp_find_hierarchy_loop_tortoise_hare( $callback, $start, $override = array(), $callback_args = array(), $_return_loop = false ) {
+    $tortoise = $hare = $evanescent_hare = $start;
+    $return = array();
+
+    // Set evanescent_hare to one past hare
+    // Increment hare two steps
+    while (
+        $tortoise
+    &&
+        ( $evanescent_hare = isset( $override[$hare] ) ? $override[$hare] : call_user_func_array( $callback, array_merge( array( $hare ), $callback_args ) ) )
+    &&
+        ( $hare = isset( $override[$evanescent_hare] ) ? $override[$evanescent_hare] : call_user_func_array( $callback, array_merge( array( $evanescent_hare ), $callback_args ) ) )
+    ) {
+        if ( $_return_loop )
+            $return[$tortoise] = $return[$evanescent_hare] = $return[$hare] = true;
+
+        // tortoise got lapped - must be a loop
+        if ( $tortoise == $evanescent_hare || $tortoise == $hare )
+            return $_return_loop ? $return : $tortoise;
+
+        // Increment tortoise by one step
+        $tortoise = isset( $override[$tortoise] ) ? $override[$tortoise] : call_user_func_array( $callback, array_merge( array( $tortoise ), $callback_args ) );
+    }
+
+    return false;
+}
+
 ?>