Type::checkEnumKey

static function checkEnumKey(array &$data, $paramName, array $enum, $default = null)
{
	if((string) $paramName != '' && array_key_exists($paramName, $data))
	{
		$enum = array_flip($enum);

		if(!isset($enum[$data[$paramName]]))
		{
			if($default !== null)
			{
				$data[$paramName] = $default;
			}
			else
			{
				unset($data[$paramName]);
				return false; // value was incorrect
			}
		}
	}

	return true; // value was correct or was replaced with the default one (which is assumed to be correct)
}