Custom permalink structure for custom post type results in 404

Question

I found some code online for creating a custom permalink for a custom post type:

add_filter('post_type_link', 'wpse33551_post_type_link', 1, 3);

    function wpse33551_post_type_link( $link, $post = 0 ){
        $timestamp = $post->post_date;
        $timestamp = preg_replace("/[^A-Za-z0-9]/", "", $timestamp);
        if ( $post->post_type == 'recipe' ){
            return home_url( 'recipe/' . $timestamp );
        } else {
            return $link;
        }
    }

    add_action( 'init', 'wpse33551_rewrites_init' );

    function wpse33551_rewrites_init(){
        add_rewrite_rule(
            'recipe/([0-9]+)?$',
            'index.php?post_type=recipe&p=$matches[1]',
            'top' );
    }

In the wordpress admin the correct url is displayed, but upon clicking the preview post button it returns a 404. I have tried flushing rewrite rules but to no avail.

Any ideas?

Answer 1

The problem with the code you've posted is that you're using the timestamp to create the permalink, and using it in add_rewrite_rule as if the timestamp was the post ID of the recipe. The p-parameter in index.php?post_type=recipe&p=$matches[1] is used for passing post ID's. Thus, WordPress will start looking for a post with an ID like "20140609070153".

Now I'm not sure why you would want a permalink such as this, but to keep a similar permalink structure that actually works, you could add the ID to the permalink structure, creating, for example, the permalink http://example.com/recipe/21-20140609070153, which is passing the post ID (21) as well.

add_filter( 'post_type_link', 'wpse33551_post_type_link', 1, 3 );

function wpse33551_post_type_link( $link, $post = 0 ) {
    $timestamp = $post->post_date;
    $timestamp = preg_replace("/[^A-Za-z0-9]/", "", $timestamp);

    if ( $post->post_type == 'recipe' ) {
        return home_url( 'recipe/' . $post->ID . '-' . $timestamp );
    }
    else {
        return $link;
    }
}

add_action( 'init', 'wpse33551_rewrites_init' );

function wpse33551_rewrites_init() {
    add_rewrite_rule(
        'recipe/([0-9]+)\-([0-9]+)?$',
        'index.php?post_type=recipe&p=$matches[1]',
        'top'
    );
}

A problem with this solution is that it would yield a valid page for any timestamp appended.

Concluding: I would move to another permalink structure, actually uniquely identifying a post (which a timestamp doesn't) :-).