code: public function handle($signal) {
  			if (isset($this->_bySignal[$signal])) {
  				/** @var Listener $reg */
  				foreach ($this->_bySignal[$signal] as $reg) {
  					$reg->interrupt = $signal;
  				}
  			} else {
  				return SIG_DFL;
  			}
  		}
docs: Signal handler for all registrations.
  
  @param $signal
  @return int