<?php
$miwen="a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws";
//被加密的字符串
function encode($str){
    $_o=strrev($str);
    // echo $_o;
        
    for($_0=0;$_0<strlen($_o);$_0++){
        $_c=substr($_o,$_0,1);
        //每次取字符串$_o的首位
        $__=ord($_c)+1;
        //转换成ASCII编码后加一
        $_c=chr($__);
        $_=$_.$_c;   
        //进行字符串拼接
    } 
    return str_rot13(strrev(base64_encode($_)));
    //进行一次base64编码后反转字符串后进行一次ROT13编码
    //https://www.runoob.com/php/func-string-strrev.html
    //https://www.runoob.com/php/func-string-str-rot13.html

}

highlight_file(__FILE__);
/*
   逆向加密算法，解密$miwen就是flag
*/
?>

<?php
$str = "a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws";
$str =  base64_decode(strrev(str_rot13($str)));
$_o = strrev($str);
for($_0=0;$_0<strlen($_o);$_0++){
        $_c=substr($_o,$_0,1);
        $__=ord($_c)-1;
        $_c=chr($__);
        $_=$_.$_c;
}
echo $_;
//代码几乎没变就是把+1变成了-1,同时把字符串编码的顺序换了一下
?>