How do I turn on the PHP error reporting in Zend Framework 2?

Everytime I receive an error in Zend Framework 2, I get just 500 Internal Server Error displayed and have to search through the Zend Server error log. I've tried putting this to my config/autoload/local.php file but it doesn't work:

return array(
    'phpSettings' => array(
        'display_startup_errors' => true,
        'display_errors' => true,
        ),
);