Nie wieder ein Beitragsbild vergessen – der Featured-Image-Reminder

add_action('save_post', 'evolution_check_thumbnail');
add_action('admin_notices', 'evolution_thumbnail_error');
function evolution_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', 'evolution_check_thumbnail');
// update the post set it to draft
wp_update_post(array('ID' => $post_id, 'post_status' => 'draft'));
add_action('save_post', 'evolution_check_thumbnail');
} else {
delete_transient( "has_post_thumbnail" );
}
}
function evolution_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>Sie müssen ein Beitragsbild festkegen. </strong>Ohne Beitragsbild kann dieser Beitrag nicht veröffentlicht werden.</p></div>";
delete_transient( "has_post_thumbnail" );
}
}