log memory usage of a Symfony2 action

SomeController.php

<?php

class SomeController extends Controller
{
    public function someAction()
    {
        $dispatcher = $this->get('event_dispatcher');
        $dispatcher->addListener('kernel.response', function (\Symfony\Component\EventDispatcher\Event $event) {
            file_put_contents(
                '/tmp/memory_logger.txt',
                date("Y-m-d H:i:s") . ' used ' . number_format(memory_get_usage() / 1024 / 1024, 2) . " MB\n",
                FILE_APPEND
            );
        });

        /* your actual code ... */
    }
}