src/Daemon/Listener.php
public function setSignalHandler(int $signal, callable $closure = null){
        if (empty($closure)){
            return pcntl_signal($signal, array($this, 'sigHandler'));
        }
        return pcntl_signal($signal, $closure);
    }
public function setSignalHandler(int $signal, callable $closure = null){
        if (empty($closure)){
            return pcntl_signal($signal, array($this, 'sigHandler'));
        }
        return pcntl_signal($signal, $closure);
    }
Sets the signal to be handled by either the closure or the built in
signal handler.

@param int $signal
@param callable|null $closure

@return bool