Formatter::numberContainsNationalPrefix

static function numberContainsNationalPrefix($phoneNumber, $nationalPrefix, $countryMetadata)
{
	if($nationalPrefix == '')
	{
		return false;
	}

	if (mb_strpos($phoneNumber, $nationalPrefix) === 0)
	{
		// Some Japanese numbers (e.g. 00777123) might be mistaken to contain the national prefix
		// when written without it (e.g. 0777123) if we just do prefix matching. To tackle that, we
		// check the validity of the number if the assumed national prefix is removed (777123 won't
		// be valid in Japan).
		$a = mb_substr($phoneNumber, mb_strlen($nationalPrefix));

		return Parser::getInstance()->parse($a, $countryMetadata['id'])->isValid();
	}
	else
	{
		return false;
	}
}