php结合md5的加密解密算法实例

<?php
/*
* Created on 2016-9-30
*
*/
function encrypt($data, $key)
{
 $key = md5($key);
  $x = 0;
  $len = strlen($data);
  $l = strlen($key);
  for ($i = 0; $i < $len; $i++)
  {
    if ($x == $l)
    {
     $x = 0;
    }
    $char .= $key{$x};
    $x++;
  }
  for ($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);
  for ($i = 0; $i < $len; $i++)
  {
    if ($x == $l)
    {
     $x = 0;
    }
    $char .= substr($key, $x, 1);
    $x++;
  }
  for ($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 = '中文网www.php.cn'; // 被加密信息
$data=iconv("gbk","utf-8",$data);
$key = 'www.jb51.net';   // 密钥
$encrypt = encrypt($data, $key);
$decrypt = decrypt($encrypt, $key);
echo $encrypt, "<br/>", $decrypt;
?>

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中文网www.php.cn