PHP Manual Function Reference Process Control Extensions Ev EvWatcher EvWatcher::setCallback EvWatcher::keepalive EvWatcher::start EvWatcher::setCallback (PECL ev >= 0.2.0)EvWatcher::setCallback — Sets new callback for the watcher Description public void EvWatcher::setCallback ( callable $callback ) Sets new callback for the watcher Parameters callback See Watcher callbacks . Return Values No value is returned.