php利用crypt函数加密和解密

// +----------------------------------------------------------------------+
// | Wiki Framework |
// +----------------------------------------------------------------------+
// $string 明文 或 密文 必填
// $isEncrypt 是否加密 可选,默认为加密
// $key 密匙 可选,默认为空格
// $b = dencrypt($a,TRUE,'123'); 
// $c = dencrypt($b,false,'123');
// 采用SHA1生成密匙簿,超过300个字符使用ZLIB压缩
function dencrypt($string, $isEncrypt = true, $key = KEY_SPACE) {
    if (!isset($string{0}) || !isset($key{0})) {
        return false;
    }
    $dynKey = $isEncrypt ? hash('sha1', microtime(true)) : substr($string, 0, 40);
    $fixedKey = hash('sha1', $key);
    $dynKeyPart1 = substr($dynKey, 0, 20);
    $dynKeyPart2 = substr($dynKey, 20);
    $fixedKeyPart1 = substr($fixedKey, 0, 20);
    $fixedKeyPart2 = substr($fixedKey, 20);
    $key = hash('sha1', $dynKeyPart1 . $fixedKeyPart1 . $dynKeyPart2 . $fixedKeyPart2);
    $string = $isEncrypt ? $fixedKeyPart1 . $string . $dynKeyPart2 : (isset($string{339}) ? gzuncompress(base64_decode(substr($string, 40))) : base64_decode(substr($string, 40)));
    $n = 0;
    $result = '';
    $len = strlen($string);
    for ($n = 0; $n < $len; $n++) {
        $result .= chr(ord($string{$n}) ^ ord($key{$n % 40}));
    }
    return $isEncrypt ? $dynKey . str_replace('=', '', base64_encode($n > 299 ? gzcompress($result) : $result)) : substr($result, 20, -20);
}