php结合md5的加密解密算法实例

<?php
/*
* Created on 2016-12-22
*
*/
function encrypt($data, $key){
　 $key = md5($key);
　 $x = 0;
　$len = strlen($data);
$l = strlen($key);
$char = "";
for ($i = 0; $i < $len; $i++){
if ($x == $l){
$x = 0;
}
$char .= $key{$x};
$x++;
}
$str = "";
for ($i = 0; $i < $len; $i++){
$str .= chr(ord($data{$i}) + (ord($char{$i})) % 256);
}
return base64_encode($str);
}
function decrypt($data, $key){
$key = md5($key);
$x = 0;
$data = base64_decode($data);
$len = strlen($data);
$l = strlen($key);
$char = "";
for ($i = 0; $i < $len; $i++){
if ($x == $l){
$x = 0;
}
$char .= substr($key, $x, 1);
$x++;
}
$str = "";
for ($i = 0; $i < $len; $i++){
if (ord(substr($data, $i, 1)) < ord(substr($char, $i, 1))){
$str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));
} else {
$str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));
}
}
return $str;
}
$data = '百度baidu.com'; // 被加密信息
$data=iconv("gbk","utf-8",$data);
$key = 'www.baidu.com';   // 密钥
$encrypt = encrypt($data, $key);
$decrypt = decrypt($encrypt, $key);
echo $encrypt, "<br/>", $decrypt;
?>