(PECL ev >= 0.2.0)
EvLoop::periodic — Creates EvPeriodic watcher object associated with the current event loop instance
$offset
   ,$interval
   ,$callback
   ,$data
     = null
   ,$priority
     = 0
   Creates EvPeriodic watcher object associated with the current event loop instance
All parameters have the same maening as for EvPeriodic::__construct()
Returns EvPeriodic object on success.
