public static function _decryptAESPKCS7($str, $key = _CryptConfig::AES_KEY, $cipher = _CryptConfig::CIPHER, $mode = _CryptConfig::MODE) {
        $key = self::_chopKeyForAES($key);
        $ivLength = self::_getBase64IVLength($cipher, $mode);
        $iv = substr($str, 0, $ivLength - 1);
        $iv = base64_decode($iv);
        $str = substr($str, $ivLength - 1);
        $str = base64_decode($str);
        $str = mcrypt_decrypt($cipher, $key, $str, $mode, $iv);
        $block = mcrypt_get_block_size($cipher, $mode);
        $pad = ord($str[($len = strlen($str)) - 1]);
        return substr($str, 0, strlen($str) - $pad);
    }