在做项目时经常会遇到加密与解密，例如用户注册后会发一封邮件到邮箱，点击邮件中的链接激活账号，这是就需要用到加密与解密。在加密与解密时经常会遇到一个问题，就是密匙中可能会有加号，在解密的时候就解密不了，原因是遇到加号就相当于密匙结束了，下面这段加密代码，经过修改后已完美解决了这个问题：

/*加密函数内部调用函数*/  
function keyED($txt,$encrypt_key) {    
    $encrypt_key = md5($encrypt_key);    
    $ctr=0;    
    $tmp = "";    
    for ($i=0;$i<strlen($txt);$i++) {    
    if ($ctr==strlen($encrypt_key)) $ctr=0;    
    $tmp.= substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1);    
    $ctr++;    
    }    
    return $tmp;    
}   
  
/*发送邮件中连接地址的加密函数*/      
function inner_DYEncrypt( $encryptstr ){   
    return  urlencode(inner_DYEncrypt_subfun($encryptstr));   
}   
  
function inner_DYEncrypt_subfun($encryptstr){   
    srand((double)microtime()*1000000);    
    $encrypt_key = md5(rand(0,32000));    
    $ctr=0; $tmpstr = "";    
    for ($i=0;$i<strlen($encryptstr);$i++){    
        if ($ctr==strlen($encrypt_key)) $ctr=0;    
        $tmpstr.= substr($encrypt_key,$ctr,1) .    
        (substr($encryptstr,$i,1) ^ substr($encrypt_key,$ctr,1));    
        $ctr++;    
    }    
    $returninfo = base64_encode(keyED($tmpstr,ENCRYPTKEY));    
    if (strrpos($returninfo,"/") or strrpos($returninfo,'') or strrpos($returninfo,'+'))   
        return inner_DYEncrypt_subfun( $encryptstr );   
    return $returninfo;   
       
}   
  
/*发送邮件中连接地址的解密函数*/      
function inner_DYDecrypt( $decryptstr ){   
    $decryptstr = urldecode($decryptstr);   
    $decryptstr = keyED(base64_decode($decryptstr),ENCRYPTKEY);    
    $tmpstr = "";    
    for ($i=0;$i<strlen($decryptstr);$i++){    
        $md5 = substr($decryptstr,$i,1);    
        $i++;    
        $tmpstr.= (substr($decryptstr,$i,1) ^ $md5);    
    }   
    return  $tmpstr;    
}   
  
/*演示*/  
    $key = "rdid=5135"; //待加密的字符串   
    echo "待加密的字符串：".$key."";   
    $key = inner_DYEncrypt($key);   
    echo "加密后的字符串：".$key."";   
    echo "解密后的字符串：".inner_DYDecrypt($key);   
  
?>