PHP实现的加密解密处理类

<?php
 /*===========================================================
 = 版权协议：
 = gpl (the gnu general public license version 2, june 1991)
 =------------------------------------------------------------
 = 文件名称：cls.sys_crypt.php
 = 摘  要：php加密解密处理类
 = 版  本：1.0
 = 参  考：discuz论坛的passport相关函数
 =------------------------------------------------------------
 = 最后更新日期：2007-12-09
 ============================================================*/
 class syscrypt {
 private $crypt_key;
 // 构造函数
 public function __construct($crypt_key) {
  $this -> crypt_key = $crypt_key;
 }
 public function php_encrypt($txt) {
  srand((double)microtime() * 1000000);
  $encrypt_key = md5(rand(0,32000));
  $ctr = 0;
  $tmp = '';
  for($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(self::__key($tmp,$this -> crypt_key));
 }
 public function php_decrypt($txt) {
  $txt = self::__key(base64_decode($txt),$this -> crypt_key);
  $tmp = '';
  for($i = 0;$i < strlen($txt); $i++) {
   $md5 = $txt[$i];
   $tmp .= $txt[++$i] ^ $md5;
  }
  return $tmp;
 }
 private function __key($txt,$encrypt_key) {
  $encrypt_key = md5($encrypt_key);
  $ctr = 0;
  $tmp = '';
  for($i = 0; $i < strlen($txt); $i++) {
   $ctr = $ctr == strlen($encrypt_key) ? 0 : $ctr;
   $tmp .= $txt[$i] ^ $encrypt_key[$ctr++];
  }
  return $tmp;
 }
 public function __destruct() {
  $this -> crypt_key = null;
 }
 }
 //执行代码
 $sc = new syscrypt('phpwms');
 $text = 'abc10000008910000000990099hh'; //需要加密的数据
 print($sc -> php_encrypt($text)); //加密
 print('<br>');
 print($sc -> php_decrypt($sc -> php_encrypt($text))); //解密
?>