gistfile1.txt

public function check_cache() {
    $group_handles = array();
    
    foreach ( $this->queue as $group => $assets  ) {
        $group_handles[] = $this->get_concatenated_filename( $group );
    }
    
    $cache_dir = trailingslashit( $this->cache_dir );
    
    if ( is_dir( $cache_dir ) ) {
        foreach( scandir( $cache_dir ) as $cached_src ) {
            if ( ! in_array( $cached_src, $group_handles ) ) {
                unlink( $cache_dir . DIRECTORY_SEPARATOR . $cached_src );   
            }
        }
    }