Encryption and decryption string function source code in PHP

PHP中加密解密字符串函数源代码：

        /**
 *Function: Encrypt string
 *Parameter 1: Content to be encrypted
 *Parameter 2: Key
*/
    function passport_encrypt($str,$key){ //加密函数
    srand((double)microtime() * 1000000);
    $encrypt_key=md5(rand(0, 32000));
    $ctr=0;
    $tmp='';
    for($i=0;$i    $ctr=$ctr==strlen($encrypt_key)?0:$ctr;
    $tmp.=$encrypt_key[$ctr].($str[$i] ^ $encrypt_key[$ctr++]);
    }
    return base64_encode(passport_key($tmp,$key));
    }
    /**
 *Function: Decrypt string
 *Parameter 1: ciphertext to be decrypted
 *Parameter 2: Key
*/
    function passport_decrypt($str,$key){ //解密函数
    $str=passport_key(base64_decode($str),$key);
    $tmp='';
    for($i=0;$i    $md5=$str[$i];
    $tmp.=$str[++$i] ^ $md5;
    }
    return $tmp;
    }
    /**
 *Auxiliary function
*/
    function passport_key($str,$encrypt_key){
    $encrypt_key=md5($encrypt_key);
    $ctr=0;
    $tmp='';
    for($i=0;$i    $ctr=$ctr==strlen($encrypt_key)?0:$ctr;
    $tmp.=$str[$i] ^ $encrypt_key[$ctr++];
    }
    return $tmp;
    }
    $str='作者：uphtm.com;
    $key='uphtm.com';
    $encrypt=passport_encrypt($str,$key);
    $decrypt=passport_decrypt($encrypt,$key);
    echo '原文：',$str."";
    echo '密文：',$encrypt."";
    echo '译文：',$decrypt."";
    ?>

加密解密, PHP