Wordpress: Custom post type with post_id-only in URLs

wordpress-ctp-post_id-only.php

/**
 * Replace 'mycustomname' with the actual custom type post
 * name to fit your needs.
 * 
 * !! Flush rewrite rules in Wordpress backend afterwards !!
 */


/**
 * Create the CTP
 */
function create_post_type_mycustomname() {
    $args = array(
        'capability_type' => 'post',
        'has_archive' => 'mycustomname',
        'rewrite' => array(
            'slug' => '/mycustomname',
            'feeds' => false
        )
    );

    register_post_type('ctp_mycustomname', $args);
}
add_action('init', 'create_post_type_mycustomname');


/**
 * Correct post links for CTP
 */
function mycustomname_links($post_link, $post = 0) {
    if($post->post_type === 'ctp_mycustomname') {
        return home_url('mycustomname/' . $post->ID . '/');
    }
    else{
        return $post_link;
    }
}
add_filter('post_type_link', 'mycustomname_links', 1, 3);


/**
 * Rewrite rules for the CTP
 */
function mycustomname_rewrites_init(){
    add_rewrite_rule('mycustomname/([0-9]+)?$', 'index.php?post_type=ctp_mycustomname&p=$matches[1]', 'top');
}
add_action('init', 'mycustomname_rewrites_init');