Super simple, ugly and insecure PHP script for sharing files

library.php

<form enctype="multipart/form-data" method="POST">
        <input type="file" name="upload"/>
        <input type="submit" value="Submit"/>
</form>

<?php

$uploads_dir = "uploads/";
if($_SERVER['REQUEST_METHOD'] == 'POST'){
        if(move_uploaded_file($_FILES['upload']['tmp_name'], $uploads_dir . basename($_FILES['upload']['name']))){
                echo '<p>Upload successful</p>';
        } else {
                echo '<p>Upload failed</p>';
        }
}

$files = scandir($uploads_dir);
echo "<ul>";
foreach($files as $f) {
        if($f[0] == '.')
                continue;
        echo "<li><a href='$uploads_dir/$f'>$f</a></li>";
}
echo "</ul>";