One shall note, that callback function MUST either return a valid Gearman status code, or return nothing (do not return).I.e. these are valid complete callbacks:<?phpfunction goodCallbackOne(GearmanTask $task){ print_r($task);}?><?phpfunction goodCallbackTwo(GearmanTask $task){ print_r($task); return GEARMAN_SUCCESS;}?>While following is NOT, unless you want your client code to fail with Gearman error 'german wait:no active file descriptors':<?phpfunction badCallbackTwo(GearmanTask $task){ print_r($task); return true;}?>