Как разрешить Apache отправлять 500 в случае ошибки PHP?

I'm developing a PHP application that uses HTTP response codes for communication as well as response bodies. So this is a typical scenario in the PHP code:

try {
    doSomething();
}
catch (Exception $e) {
    header('HTTP/1.1 500 Internal Server Error');
}

... and the typical code in clients looks like:

switch(responseCode) {
     case 200 :
         // all fine
         // ....
     case 500 :
         // trouble!
 } 

This is cool, as long as every error is well caught in PHP code.

The problem: If, for any reason in the php code occures an uncaught error or an uncatchable error like syntax errors, Apache will send 200 OK. But I wan't apache to say 500 Internal Server Error. Maybe per .htaccess or so.