Interop\Async\Loop::onSignal PHP Method

    public static function onSignal($signo, callable $callback, $data = null)
    {
        $driver = self::$driver ?: self::get();
        return $driver->onSignal($signo, $callback, $data);
    }

 public function run(Container $container, callable $action)
 {
     $logger = LoopConfig::getLogger();
     if ($this->running === 0) {
         foreach ($this->loggers as $handler) {
             $logger->addHandler($handler);
         }
     }
     $this->running++;
     try {
         $buffer = '';
         if ($this->ipc) {
             ob_start(function (string $data, int $phase) use(&$buffer) {
                 $buffer .= $data;
                 return '';
             }, 1, \PHP_OUTPUT_HANDLER_FLUSHABLE);
         }
         Loop::execute(function () use($container, $action, $logger, &$buffer) {
             Loop::setErrorHandler(function (\Throwable $e) use($logger) {
                 $logger->critical('', ['exception' => $e]);
             });
             $watcher = Loop::repeat(500, function () use(&$buffer, $logger) {
                 if ($buffer !== '') {
                     try {
                         $this->ipc->sendOutput($buffer);
                     } finally {
                         $buffer = '';
                     }
                 }
             });
             Loop::unreference($watcher);
             if ($this->contextName === 'development') {
                 $locator = $container->get(ResourceLocator::class);
                 $watcher = Loop::repeat(5000, function () use($locator) {
                     $locator->syncFiles();
                 });
                 Loop::unreference($watcher);
             }
             if ($this->ipc) {
                 $this->ipc->run();
             }
             $signal = function () {
                 if ($this->ipc) {
                     $this->ipc->stop();
                 }
                 Loop::stop();
             };
             // Shutdown on SIGTERM.
             try {
                 Loop::onSignal(15, $signal);
             } catch (UnsupportedFeatureException $e) {
                 // signal handling is not available...
             }
             $action();
         });
     } finally {
         if ($this->ipc) {
             \ob_end_clean();
         }
         $this->running--;
         if ($this->running === 0) {
             foreach ($this->loggers as $handler) {
                 $logger->removeHandler($handler);
             }
         }
     }
 }