Rewrite Post Type URLs in WordPress

class-permaposttype.php

<?php
if ( ! defined( ABSPATH ) ) exit;

if ( ! class_exists( 'PermaPostType' ) ) {

	class PermaPostType {

		/**
		 * Initialise
		 */
		function init() {

			// rewrite
			add_action( 'init', array( $this, 'rewrite' ) );

			// mod query
			add_filter( 'query_vars', array( $this, 'query_vars' ) );

			// nicer link
			add_filter( 'post_type_link', array( $this, 'permalink' ), 10, 4 );
		}

		/**
		 * Rewrite the urls
		 */
		function rewrite() {

			// the structure
			$structure = '/%listid%/%listtitle%/';

			// add the structure
			add_permastruct( 'listing', $structure, false );

			// create tags that WP can understand (for the urls only)
			add_rewrite_tag( "%listid%", '([^/]\d+)', "p=" );
			add_rewrite_tag( "%listtitle%", '([^/]+)', "listtitle=" );

			// modify the query for variables (for actual processes)
			add_action( 'pre_get_posts', array( $this, 'query' ) );
		}

		/**
		 * Just add to the standard var array, so WordPress will add it to the array
		 * 
		 * @param array $query_vars Default query args
		 * @return string
		 */
		function query_vars( $query_vars ) {

			// this is the one we set, post id is automatically set and handled
			$query_vars[] = 'listtitle';

			return $query_vars;
		}

		/**
		 * Filters the url to create a nice looking permalink
		 * 
		 * Converts http://site.com/%listid%/%listtitle%/ to
		 * 
		 * http://site.com/1234/post-title
		 * 
		 * @param string $permalink The original permalink
		 * @param object $post The current custom post
		 * @return string
		 */
		function permalink( $permalink, $post ) {

			// don't do this for other post types and unpublished stati
			if ( ('listing' != $post->post_type) || '' === $permalink || in_array( $post->post_status, array( 'draft', 'pending', 'auto-draft' ) ) ) {
				return;
			}

			// those are our tags
			$rewritecode = array(
					'%listid%',
					'%listtitle%'
			);


			$list_id = 0;

			// if there is a list id tag, replace it with post id
			if ( strpos( $permalink, '%listid%' ) !== false ) {
				$list_id = $post->ID;
			}

			$list_title = '';

			// if there is a list_title tag (even if empty) replace with post title
			if ( strpos( $permalink, '%listtitle%' ) !== false ) {
				$list_title = sanitize_title( $post->post_title );
			}

			$rewritereplace = array(
					$list_id,
					$list_title,
			);

			// the actual replacement
			$permalink = str_replace( $rewritecode, $rewritereplace, $permalink );

			return $permalink;
		}

		/**
		 * Filter the current query
		 * @param object $query The default query
		 */
		function query( $query ) {

			// only do this for our posts
			if ( isset( $query->query_vars[ 'listtitle' ] ) ) {

				// the post type doesn't get set, set it
				// otherwise we get a 404
				$query->set( 'post_type', 'listing' );
			}

			// and we're done!
		}

	}

}