JBZoo\Utils\Sys::isFunc PHP Method

    public static function isFunc($funcName)
    {
        return is_callable($funcName) || is_string($funcName) && function_exists($funcName) && is_callable($funcName);
    }

 /**
  * Stop profiler
  */
 public function stop()
 {
     $this->_endTime = microtime(true);
     $this->tick();
     if (Sys::isFunc('unregister_tick_function')) {
         unregister_tick_function(array($this, 'tick'));
     }
 }