add_action( 'save_post', 'save_post_example' );
add_action( 'admin_notices', 'admin_notices_example' );
function save_post_example( $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 admin_notices_example() {
// 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>You must select a featured image for your post.</p></div>';
delete_transient( 'has_post_thumbnail' );
}
}
