Method signal

/**
 * Method to handle POSIX signals.
 *
 * @param   integer  $signal  The received POSIX signal.
 *
 * @return  void
 *
 * @since   1.7.0
 * @see     pcntl_signal()
 * @throws  \RuntimeException
 */
public static function signal($signal)
{
    // Log all signals sent to the daemon.
    Log::add('Received signal: ' . $signal, Log::DEBUG);
    // Let's make sure we have an application instance.
    if (!is_subclass_of(static::$instance, CliApplication::class)) {
        Log::add('Cannot find the application instance.', Log::EMERGENCY);
        throw new \RuntimeException('Cannot find the application instance.');
    }
    // Fire the onReceiveSignal event.
    static::$instance->triggerEvent('onReceiveSignal', array($signal));
    switch ($signal) {
        case SIGINT:
        case SIGTERM:
            // Handle shutdown tasks
            if (static::$instance->running && static::$instance->isActive()) {
                static::$instance->shutdown();
            } else {
                static::$instance->close();
            }
            break;
        case SIGHUP:
            // Handle restart tasks
            if (static::$instance->running && static::$instance->isActive()) {
                static::$instance->shutdown(true);
            } else {
                static::$instance->close();
            }
            break;
        case SIGCHLD:
            // A child process has died
            while (static::$instance->pcntlWait($signal, WNOHANG || WUNTRACED) > 0) {
                usleep(1000);
            }
            break;
        case SIGCLD:
            while (static::$instance->pcntlWait($signal, WNOHANG) > 0) {
                $signal = static::$instance->pcntlChildExitStatus($signal);
            }
            break;
        default:
            break;
    }
}