wp_old_slug_redirect

Source code

function wp_old_slug_redirect() {

	global $wp_query;

	if ( is_404() && '' != $wp_query->query_vars['name'] ) :

		global $wpdb;



		// Guess the current post_type based on the query vars.

		if ( get_query_var('post_type') )

			$post_type = get_query_var('post_type');

		elseif ( !empty($wp_query->query_vars['pagename']) )

			$post_type = 'page';

		else

			$post_type = 'post';



		if ( is_array( $post_type ) ) {

			if ( count( $post_type ) > 1 )

				return;

			$post_type = array_shift( $post_type );

		}



		// Do not attempt redirect for hierarchical post types

		if ( is_post_type_hierarchical( $post_type ) )

			return;



		$query = $wpdb->prepare("SELECT post_id FROM $wpdb->postmeta, $wpdb->posts WHERE ID = post_id AND post_type = %s AND meta_key = '_wp_old_slug' AND meta_value = %s", $post_type, $wp_query->query_vars['name']);



		// if year, monthnum, or day have been specified, make our query more precise

		// just in case there are multiple identical _wp_old_slug values

		if ( '' != $wp_query->query_vars['year'] )

			$query .= $wpdb->prepare(" AND YEAR(post_date) = %d", $wp_query->query_vars['year']);

		if ( '' != $wp_query->query_vars['monthnum'] )

			$query .= $wpdb->prepare(" AND MONTH(post_date) = %d", $wp_query->query_vars['monthnum']);

		if ( '' != $wp_query->query_vars['day'] )

			$query .= $wpdb->prepare(" AND DAYOFMONTH(post_date) = %d", $wp_query->query_vars['day']);



		$id = (int) $wpdb->get_var($query);



		if ( ! $id )

			return;



		$link = get_permalink($id);



		if ( !$link )

			return;



		wp_redirect( $link, 301 ); // Permanent redirect

		exit;

	endif;

}