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;
?>