libphonenumber\prefixmapper\PhonePrefixMap::lookupKey PHP Метод

    public function lookupKey($key)
    {
        if (count($this->phonePrefixMapStorage) == 0) {
            return null;
        }
        while (strlen($key) > 0) {
            if (array_key_exists($key, $this->phonePrefixMapStorage)) {
                return $this->phonePrefixMapStorage[$key];
            }
            $key = substr($key, 0, -1);
        }
        return null;
    }