强大的PHP加密解密类

class Ender{
private $enkey;//加密解密用的密钥
//构造参数是密钥
public function __construct($key=''){
if(!$key){
$this->enkey=$key;
}
}
//设置密钥
public function set_key($key){
$this->enkey=$key;
}
private function keyED($txt,$encrypt_key)
{
$encrypt_key = md5($encrypt_key);
$ctr=0;
$tmp = "";
for ($i=0;$i{
if ($ctr==strlen($encrypt_key)) $ctr=0;
$tmp.= substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1);
$ctr++;
}
return $tmp;
}
//加密字符串
public function encrypt($txt,$key='')
{
if(!$key){
$key=$this->enkey;
}
srand((double)microtime()*1000000);
$encrypt_key = md5(rand(0,32000));
$ctr=0;
$tmp = "";
for ($i=0;$i{
if ($ctr==strlen($encrypt_key)) $ctr=0;
$tmp.= substr($encrypt_key,$ctr,1) .
(substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1));
$ctr++;
}
return base64_encode($this->keyED($tmp,$key));
}
//解密字符串
public function decrypt($txt,$key='')
{
$txt=base64_decode($txt);
if(!$key){
$key=$this->enkey;
}
$txt = $this->keyED($txt,$key);
$tmp = "";
for ($i=0;$i{
$md5 = substr($txt,$i,1);
$i++;
$tmp.= (substr($txt,$i,1) ^ $md5);
}
return $tmp; 
}
}