/**
  * Flush proxy caches.
  *
  * ## OPTIONS
  *
  * [--cache=<url>]
  * : The name of the person to greet.
  *
  * [--format=<format>]
  * : Accepted values: csv, json. Default: csv
  *
  * ## EXAMPLES
  *
  *     wp nginx list --format=json
  *     wp nginx flush
  *     wp nginx flush --cache=http://example.com/archives/10
  *
  * @synopsis [--cache=<url>]
  * @subcommand flush
  */
 function flush($args, $assoc_args)
 {
     global $nginxchampuru;
     if (isset($assoc_args['cache']) && $assoc_args['cache']) {
         $id = url_to_postid($assoc_args['cache']);
         if ($id) {
             NginxChampuru_FlushCache::flush_by_post($id);
             WP_CLI::success("Proxy caches are flushed on " . $assoc_args['cache']);
             exit;
         } else {
             WP_CLI::error('Cache url is not found.');
             exit;
         }
     } else {
         $nginxchampuru->transientExec("flush_cache", 'all', 0);
         WP_CLI::success("All proxy caches are flushed.");
         exit;
     }
 }