Event callbacks

If a callback is registered for an event, it will be called when the event becomes active. To associate a callback with event one can pass a callable to whether Event::__construct() , or Event::set() , or one of the factory methods like Event::timer() .

An event callback should match the following prototype:

void callback ([ mixed $fd = NULL [, int $what [, mixed $arg = NULL ]]] )

fd: The file descriptor, stream resource or socket associated with the event. For signal event fd is equal to the signal number.
what: Bit mask of all events triggered.
arg: User custom data.

Event::timer() expects the callback to match the following prototype:

void callback ([ mixed $arg = NULL ] )

arg: User custom data.

Event::signal() expects the callback to match the following prototype:

void callback ([ int $signum [, mixed $arg = NULL ]] )

signum: The number of the triggered signal(e.g. SIGTERM ).
arg: User custom data.