【攻防世界】web2（逆向解密）

<?php
$miwen="a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws";
function encode($str){
    $_o=strrev($str);
    // echo $_o;
        
    for($_0=0;$_0<strlen($_o);$_0++){
       
        $_c=substr($_o,$_0,1);
        $__=ord($_c)+1;
        $_c=chr($__);
        $_=$_.$_c;   
    } 
    return str_rot13(strrev(base64_encode($_)));
}
highlight_file(__FILE__);
/*
   逆向加密算法，解密$miwen就是flag
*/
?>

<?php 
    function decode($str) {
        $result = "";
        $str = str_rot13($str);
        $str = strrev($str);
        $str = base64_decode($str);
        
        for($i = 0; $i < strlen($str); $i++) {
            $part = substr($str, $i, 1);
            $trans = ord($part) - 1;
            $part = chr($trans);
            $result = $result.$part;
        }
        return strrev($result);
    }
    $miwen="a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws";
    echo decode($miwen);
?>