All watchers can be active(waiting for events) or inactive(paused). Only
active watchers will have their callbacks invoked. All callbacks will be
called with at least two arguments:
watcher - the watcher, and
revents a bitmask of received events.
Watcher callbacks are passed to the watcher constructors (the classes derived from EvWatcher - EvCheck::__construct , EvChild::__construct etc.). A watcher callback should match the following prototype:
$watcher = NULL [, int
$revents = NULL ]] )
The watcher instance(of a class extending EvWatcher ).
Watcher received events .
Each watcher type has its associated bit in
revents , so one can use
the same callback for multiple watchers. The event mask is named after
the type, i.e. EvChild (or EvLoop::child ) sets
EV::CHILD , EvPrepare (or EvLoop::prepare ) sets
EvPeriodic (or EvLoop::periodic ) sets
so on, with the exception of I/O events (which can set both