comment demander une image avant de pouvoir publier un article wordpress

1<?php
2add_action('save_post', 'wpds_check_thumbnail');
3add_action('admin_notices', 'wpds_thumbnail_error');
4function wpds_check_thumbnail($post_id) {
5    // change to any custom post type
6    if(get_post_type($post_id) != 'post')
7        return;
8    if ( !has_post_thumbnail( $post_id ) ) {
9        // set a transient to show the users an admin message
10        set_transient( "has_post_thumbnail", "no" );
11        // unhook this function so it doesn't loop infinitely
12        remove_action('save_post', 'wpds_check_thumbnail');
13        // update the post set it to draft
14        wp_update_post(array('ID' => $post_id, 'post_status' => 'draft')); 
15        add_action('save_post', 'wpds_check_thumbnail');
16    } else {
17        delete_transient( "has_post_thumbnail" );
18    }
19}
20function wpds_thumbnail_error()
21{
22    // check if the transient is set, and display the error message
23    if ( get_transient( "has_post_thumbnail" ) == "no" ) {
24        echo "<div id='message' class='error'><p><strong>You must select Featured Image. Your Post is saved but it can not be published.</strong></p></div>";
25        delete_transient( "has_post_thumbnail" );
26    } 
27}
28?>