(PECL gearman >= 0.5.0)
GearmanClient::setCreatedCallback — Set a callback for when a task is queued
Sets a function to be called when a task is received and queued by the Gearman job server. The callback should accept a single argument, a GearmanClient oject.
A function to call
成功时返回 TRUE, 或者在失败时返回 FALSE.