Symfony2: __toString() must not throw an exception - symfony

Question

I am deploying my Symfony2 application, but I am getting the following error:
FatalErrorException in classes.php line 0:
Error: Method Symfony\Component\HttpFoundation\Request::__toString() must not throw an exception
Apache is slightly more descriptive, stating something about Monolog:
PHP Fatal error: Method Symfony\\Component\\HttpFoundation\\Request::__toString() must not throw an exception in /my/path/vendor/monolog/monolog/src/Monolog/Formatter/NormalizerFormatter.php on line 0
It is also the only thing It is not clear to me how this is happening. Dev-environment on my local machine is running fine.
I have tried to clear the prod cache, the composer cache and restarted apache service. I also did a fresh "composer install" after clearing its cache.
Anyone has an idea how this can be solved? Am running Symfony v2.7.4.

Answer 1

You should to check your $_COOKIE or $_SESSION for example;
The trouble is you could have array value in $_COOKIE, so on your debug environment you could fall into the following situation:
Debug::enable() //see, i don't exclude E_NOTICE here
$request = Request::createFromGlobals();
echo $request->__toString();
//so, from now you've got your Exception because of
//Debug package converts E_NOTICE to Fatal
//which turns into Exception
So if you want to fix this trouble you need to:
find the real reason of exception triggering (notice, deprecated, strict message, etc)
exclude it from Debug: Debug::enable(~E_NOTICE);
OR just remove (string)$request from your code if possible;
see Request code:
//part of __toString() method
foreach ($this->cookies as $k => $v) {
$cookies[] = $k.'='.$v;
}