PHP encryption and decryption function code implementation example

<?php

//加密函数
function passport_encrypt($txt, $key) {
    srand((double)microtime() * 1000000);
    $encrypt_key = md5(rand(0, 32000));
    $ctr = 0;
    $tmp = &#39;&#39;;
    for($i = 0;$i < strlen($txt); $i++) {
       $ctr = $ctr == strlen($encrypt_key) ? 0 : $ctr;
       $tmp .= $encrypt_key[$ctr].($txt[$i] ^ $encrypt_key[$ctr++]);
    }
    return base64_encode(passport_key($tmp, $key));
}
//解密函数
function passport_decrypt($txt, $key) {
    $txt = passport_key(base64_decode($txt), $key);
    $tmp = &#39;&#39;;
    for($i = 0;$i < strlen($txt); $i++) {
       $md5 = $txt[$i];
       $tmp .= $txt[++$i] ^ $md5;
    }
    return $tmp;
}
//上面两个函数用到的公共函数
function passport_key($txt, $encrypt_key) {
    $encrypt_key = md5($encrypt_key);
    $ctr = 0;
    $tmp = &#39;&#39;;
    for($i = 0; $i < strlen($txt); $i++) {
       $ctr = $ctr == strlen($encrypt_key) ? 0 : $ctr;
       $tmp .= $txt[$i] ^ $encrypt_key[$ctr++];
    }
    return $tmp;
}

//----------------------------------------
//----------------------------------------
//-------------示例-----------------------
//----------------------------------------
//----------------------------------------
//
$str = &#39;你好，我是+-!少林a b张三丰&#39;;
echo &#39;<br>------key:aaa----------<br>&#39;;
echo $x = passport_encrypt($str,&#39;aaa&#39;);
//值会变，其中一个如下 
//AOdS7lWlU+IM+1fnALBV5QOOV7dchQfEX+MCwgf2U3BXeQcnVuNavgPAA+hbmlLJAWEHIVRnD7hYvgf/U+lS4gCKUrdVvVO3
echo &#39;<br>-----------------------<br>&#39;;
echo passport_decrypt($x,&#39;aaa&#39;); 
echo &#39;<br><br><br><br><br><br><br><br><br><br><br><br>&#39;;

echo &#39;<br>------key:bbb----------<br>&#39;;
echo $y = passport_encrypt($str,&#39;bbb&#39;);
//值会变，其中一个如下
//Ae0F5gD1C+oB9wC/DOZZ6AeKU7MCjleWUbEAmFGuAi4JLF8gUeFW4lKQUrYBmlrAA2MHIVcxBrMFv1PzXOha5QGABb8A7Qu/
echo &#39;<br>-----------------------<br>&#39;;
echo passport_decrypt($y,&#39;bbb&#39;);

?>

<?php
//加解密字符串函数，可以加密中文
/*
//加密
echo $encode = authcode(&#39;爱迪生&#39;, &#39;ENCODE&#39;, &#39;3&#39;); //DvAHOdGFqa8xK4CDLnbr2mE
//解密
echo $decode = authcode($encode, &#39;DECODE&#39;, &#39;3&#39;); //爱迪生
//密钥
$auth_key = 34577;
参数：$string字符串，$operation加密还是解密，$key密钥
*/
function authcode($string, $operation, $key = &#39;&#39;)
{
    $key = md5($key ? $key : $GLOBALS[&#39;auth_key&#39;]);
    $key_length = strlen($key);
    $string = $operation == &#39;DECODE&#39; ? base64_decode($string) : substr(md5($string . $key), 0, 8) . $string;
    $string_length = strlen($string);
    $rndkey = $box = array();
    $result = &#39;&#39;;
    for ($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 ($operation == &#39;DECODE&#39;) {
        if (substr($result, 0, 8) == substr(md5(substr($result, 8) . $key), 0, 8)) {
            return substr($result, 8);
        } else {
            return &#39;&#39;;
        }
    } else {
        return str_replace(&#39;=&#39;, &#39;&#39;, base64_encode($result));
    }
}
?>