php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 = 'www.gdcool.net'; //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
?>