Obscenely Simple PHP File Upload

index.php

<?php
define("UPLOAD_DIR", "./");
ini_set("upload_max_filesize", "200M");
ini_set("post_max_size", "200M");

if (!empty($_FILES["myFile"])) {
    $myFile = $_FILES["myFile"];

    if ($myFile["error"] !== UPLOAD_ERR_OK) {
        echo "<p>An error occurred.</p>";
        exit;
    }

    // ensure a safe filename
    $name = preg_replace("/[^A-Z0-9._-]/i", "_", $myFile["name"]);

    // don't overwrite an existing file
    $i = 0;
    $parts = pathinfo($name);
    while (file_exists(UPLOAD_DIR . $name)) {
        $i++;
        $name = $parts["filename"] . "-" . $i . "." . $parts["extension"];
    }

    // preserve file from temporary directory
    $success = move_uploaded_file($myFile["tmp_name"],
        UPLOAD_DIR . $name);
    if (!$success) { 
        echo "<p>Unable to save file. ".$_FILES['myFile']['error']."</p>";
        exit;
    }else{
        echo "Upload Successful! ".$name;
    }

    // set proper permissions on the new file
    chmod(UPLOAD_DIR . $name, 0644);
}

?>
<form action="/simple-upload/index.php" method="post" enctype="multipart/form-data"> 
 <input type="file" name="myFile">
 <br>
 <input id="submit" type="submit" value="Upload">
 <div id="loading" style="display:none">
    Uploading!!! Please wait.
 </div>
</form>
<script>
    document.getElementById("submit").onclick = function(){
        document.getElementById("loading").style.display = "block";
    };
</script>