Require a featured image before you can publish posts

add_action('save_post', 'wpds_check_thumbnail'); add_action('admin_notices', 'wpds_thumbnail_error'); function wpds_check_thumbnail( $post_id ) { // change to any custom post type if( get_post_type($post_id) != 'post' ) return; if ( ! has_post_thumbnail( $post_id ) ) { // set a transient to show the users an admin message set_transient( "has_post_thumbnail", "no" ); // unhook this function so it doesn't loop infinitely remove_action('save_post', 'wpds_check_thumbnail'); // update the post set it to draft wp_update_post(array('ID' => $post_id, 'post_status' => 'draft')); add_action('save_post', 'wpds_check_thumbnail'); } else { delete_transient( "has_post_thumbnail" ); } } function wpds_thumbnail_error() { // check if the transient is set, and display the error message if ( get_transient( "has_post_thumbnail" ) == "no" ) { echo "<div id='message' class='error'><p><strong>You must add a Featured Image before publishing this. Don't panic, your post is saved.</strong></p></div>"; delete_transient( "has_post_thumbnail" ); } }