move_uploaded_file() function does not upload to my folder - php

Question

I'm making a ecommerce website with a CMS where I can edit, add products etc, when I add a product and choose and image from my computer it does not upload to my folder I made for images "uploads".
Does anyone know the solution to this, it's probably in my code but I can't seem to figure it out.
If I manually add the image to the folder uploads and choose the image when I add the product the image shows.
Here is my code:
function add_product() {
if(isset($_POST['publish'])) {
$product_title = escape_string($_POST['product_title']);
$product_category_id = escape_string($_POST['product_category_id']);
$product_price = escape_string($_POST['product_price']);
$product_description = escape_string($_POST['product_description']);
$short_desc = escape_string($_POST['short_desc']);
$product_quantity = escape_string($_POST['product_quantity']);
$product_image = escape_string($_FILES['file']['name']);
$image_temp_location = escape_string($_FILES['file']['tmp_name']);
move_uploaded_file($image_temp_location, UPLOAD_DIRECTORY . DS . $product_image);
$query = query("INSERT INTO products(product_title, product_category_id, product_price, product_description, short_desc, product_quantity, product_image) VALUES('{$product_title}', '{$product_category_id}', '{$product_price}', '{$product_description}', '{$short_desc}', '{$product_quantity}', '{$product_image}')");
$last_id = last_id();
confirm($query);
set_message("New Product with id {$last_id} was Added");
redirect("index.php?products");
}
}
The UPLOAD_DIRECTORY is a path that I have configured in a file named config.php and it looks like this:
defined("UPLOAD_DIRECTORY") ? null : define("UPLOAD_DIRECTORY", __DIR__ . DS . "uploads");