upload.php Form Handling

<?php
include("index.html");
if(!empty($_POST)) {
    if(isset($_FILES["world"])) {

        $world = $_FILES["world"];

        $name = $world["name"];
        $tmp_name = $world["tmp_name"];
        $size = $world["size"];
        $ext = explode('.', $name);
        $ext = strtolower(end($ext));

        $allowed = "deep";

        if ($ext == $allowed) {
            if ($size <= 300000) {
                $id = uniqid('', true);
                $destination = 'worlds/' . $id . '.' . $ext;
                if(move_uploaded_file($tmp_name, $destination)) {
                    echo '<br/>World: "' . $name . '" uploaded to DeeperNet!';
                    echo “<br/>World ID: ” . $id;
                    $info = fopen('worlds/' . $id . '.txt', 'w');
                    fwrite($info, $_POST['name'] . "\r\n");
                    fwrite($info, $_POST['desc']);
                    fclose($info);
                }
            }
        }