(PECL gearman >= 0.5.0)
GearmanClient::setCompleteCallback — Set a function to be called on task completion
Use to set a function to be called when a GearmanTask is completed, or when GearmanJob::sendComplete() is invoked by a worker (whichever happens first).
This callback executes only when executing a GearmanTask using GearmanClient::runTasks(). It is not used for individual jobs.
callbackA function to be called
成功時(shí)返回 true， 或者在失敗時(shí)返回 false。