libphonenumber\PhoneNumberUtil::checkRegionForParsing PHP Method

    protected function checkRegionForParsing($numberToParse, $defaultRegion)
    {
        if (!$this->isValidRegionCode($defaultRegion)) {
            // If the number is null or empty, we can't infer the region.
            $plusCharsPatternMatcher = new Matcher(static::$PLUS_CHARS_PATTERN, $numberToParse);
            if ($numberToParse === null || mb_strlen($numberToParse) == 0 || !$plusCharsPatternMatcher->lookingAt()) {
                return false;
            }
        }
        return true;
    }