Callback can accept not only GearmanTask object, but it can recieve a variable from GearmanClient::addTask():<?php$client = new GearmanClient();$client->addServer();$client->setCreatedCallback(function(GearmanTask $task, $some_info) { // now we have $some_info // ...});$client->addTask($function_name, $workload, "some info");?>So, we can send to our anonymous function something like $workload, because we can't get it from GearmanTask object. It may be usefull for logging of tasks queuing.