JsonConverter::isValid

static function isValid($string)
{
	$string = trim($string);
	$char = mb_substr($string, 0, 1);
	if(!in_array($char, array('{', '[')))
	{
		return false;
	}
	$char = mb_substr($string, -1);
	if(!in_array($char, array('}', ']')))
	{
		return false;
	}

	try
	{
		$r = Json::decode($string);
		return is_array($r);
	}
	catch (ArgumentException $exception)
	{
		return false;
	}
}