PHP_加密解密字串.php

<?php
//加解密字串函式，可以加密中文
/*
//加密
echo $encode = authcode('愛迪生', 'ENCODE', '3'); //DvAHOdGFqa8xK4CDLnbr2mE
//解密
echo $decode = authcode($encode, 'DECODE', '3'); //愛迪生
//金鑰
$auth_key = 34577;
引數：$string字串，$operation加密還是解密，$key金鑰
*/
function authcode($string, $operation, $key = '')
{
    $key = md5($key ? $key : $GLOBALS['auth_key']);
    $key_length = strlen($key);
    $string = $operation == 'DECODE' ? base64_decode($string) : substr(md5($string . $key), 0, 8) . $string;
    $string_length = strlen($string);
    $rndkey = $box = array();
    $result = '';
    for ($i = 0; $i <= 255; $i++) {
        $rndkey[$i] = ord($key[$i % $key_length]);
        $box[$i] = $i;
    }
    for ($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, 8) == substr(md5(substr($result, 8) . $key), 0, 8)) {
            return substr($result, 8);
        } else {
            return '';
        }
    } else {
        return str_replace('=', '', base64_encode($result));
    }
}
?>