Authcode這個函數(shù)很多人都使用，這函數(shù)來自Discuz程序，用于加密解密字符串，可以設(shè)置鑰匙（key）和過期時間，在很多時候都用得著。原版的函數(shù)代碼可能會生成+、/、&這樣的字符，導(dǎo)致通過URL傳值取回時被轉(zhuǎn)義，導(dǎo)致無法解密?；鸲司W(wǎng)絡(luò)稍加修改，把這幾個字符替換成其它字符，解密時再替換回去，這樣就完美了！
    代碼如下:
    function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0){
    if($operation == 'DECODE') {
    $string = str_replace('[a]','+',$string);
    $string = str_replace('[b]','&',$string);
    $string = str_replace('[c]','/',$string);
    }
    $ckey_length = 4;
    $key = md5($key ? $key : 'livcmsencryption ');
    $keya = md5(substr($key, 0, 16));
    $keyb = md5(substr($key, 16, 16));
    $keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : '';
    $cryptkey = $keya.md5($keya.$keyc);
    $key_length = strlen($cryptkey);
    $string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;
    $string_length = strlen($string);
    $result = '';
    $box = range(0, 255);
    $rndkey = array();
    for($i = 0; $i <= 255; $i++) {
    $rndkey[$i] = ord($cryptkey[$i % $key_length]);
    }
    for($j = $i = 0; $i < 256; $i++) {
    $j = ($j + $box[$i] + $rndkey[$i]) % 256;
    $tmp = $box[$i];
    $box[$i] = $box[$j];
    $box[$j] = $tmp;
    }
    for($a = $j = $i = 0; $i < $string_length; $i++) {
    $a = ($a + 1) % 256;
    $j = ($j + $box[$a]) % 256;
    $tmp = $box[$a];
    $box[$a] = $box[$j];
    $box[$j] = $tmp;
    $result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256]));
    }
    if($operation == 'DECODE') {
    if((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) {
    return substr($result, 26);
    } else {
    return '';
    }
    } else {
    $ustr = $keyc.str_replace('=', '', base64_encode($result));
    $ustr = str_replace('+','[a]',$ustr);
    $ustr = str_replace('&','[b]',$ustr);
    $ustr = str_replace('/','[c]',$ustr);
    return $ustr;
    }
    }