先ほどの引用：

ここの部分を以下のように記載してみましたがエラーとなってしまいました。whileはflgが0の間繰り返すようになっているかと思うので、重複していない場合はフラグを1にしてループ抜けを、重複している場合はflgの値を変えずに再度生成という形にしている予定なのですが…
最下部にエラー情報を記載いたします。

// TODO DBを確認し、同じ注文番号がないこと。
$qb = $em->getRepository('Eccube\Entity\Order')
->createQueryBuilder('o')
->select('COUNT(o.order_number)')
->where('o.order_number = :orderId')
->setParameter('orderId', '$orderId');
$countOrderId = $qb
->getQuery()
->getSingleResult();
dump($countOrderId);

if ($countOrderId == 0) {
$flg = 1;
}

Apacheのエラーログは以下の通りです。
メモリが足りてないって感じなのですかね？？
[Thu Jun 30 09:47:43.589810 2016] [:error] [pid 11184:tid 1864] [client ::1:53964] PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 24 bytes) in C:\\xampp\\htdocs\\eccube-3.0.10\\vendor\\symfony\\http-kernel\\DataCollector\\DumpDataCollector.php on line 132, referer: http://localhost/eccube-3.0.10/html/index_dev.php/cart

以下、システムのログになります
[2016-06-30 09:48:09] eccube.DEBUG: Stored the security token in the session. {"key":"_security_customer"} []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "Silex\EventListener\MiddlewareListener::onKernelResponse". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\ResponseListener::onKernelResponse". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "closure". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "closure". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "closure". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "Eccube\EventListener\RequestDumpListener::onResponse". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "Silex\EventListener\LogListener::onKernelResponse". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\Security\Http\RememberMe\ResponseListener::onKernelResponse". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelResponse". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "Symfony\Bundle\WebProfilerBundle\EventListener\WebDebugToolbarListener::onKernelResponse". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.response" to listener "closure". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\HttpKernel\EventListener\RouterListener::onKernelFinishRequest". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.finish_request" to listener "Silex\EventListener\LocaleListener::onKernelFinishRequest". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\Security\Http\Firewall::onKernelFinishRequest". [] []
[2016-06-30 09:48:09] eccube.DEBUG: KernelEvents::TERMINATE _wdt [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.terminate" to listener "closure". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.terminate" to listener "closure". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.terminate" to listener "closure". [] []
[2016-06-30 09:48:09] eccube.DEBUG: Notified event "kernel.terminate" to listener "Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelTerminate". [] []