php file handler

<?php

$valid_passwords = array ("username" => "password");
$valid_users = array_keys($valid_passwords);

$user = $_SERVER['PHP_AUTH_USER'] ?: '' ;
$pass = $_SERVER['PHP_AUTH_PW'] ?: '';

$validated = (in_array($user, $valid_users)) && ($pass == $valid_passwords[$user]);

if (!$validated) {
  header('WWW-Authenticate: Basic realm="My Realm"');
  header('HTTP/1.0 401 Unauthorized');
  die ("Not authorized");
}

if(isset($_FILES['upload'])) {
    $target_dir = "uploads/";
    $target_file = $target_dir . basename($_FILES["upload"]["name"]);
    $target_file_ext = strtolower(pathinfo($target_file, PATHINFO_EXTENSION));
    if($target_file_ext == 'gz' || $target_file_ext == 'tgz' || $target_file_ext == 'tar') {
        if($_FILES["upload"]["size"] <= 50000000) {
            if (move_uploaded_file($_FILES["upload"]["tmp_name"], $target_file)) {
                echo "The file ". basename( $_FILES["upload"]["name"]). " has been uploaded.";
            }
            else {
                echo "Sorry, there was an error uploading your file.";
            }
        }
        
    }
}

?>