OpenCart - PHP - Check if a product (download) is already purchased - php

Question

Regarding OpenCart store selling digital downloads.
I am trying to add a script to the product page to warn the customer if that specific product (download) is already purchased and exists in Account>Downloads.
The reason is to avoid customers purchasing the same product twice.
Appreciate your help.
Edit:
I have tried getting the product IDs of all orders by a customer using a SQL query and that works fine externally but inside OpenCart I am facing issues.
A query such as:
SELECT product_id
FROM ocuk_order_product
WHERE order_id IN (
SELECT order_id
FROM ocuk_order
WHERE customer_id = 'xxxx'
)
My main problem is not being sure how to get similar results in OpenCart Product page. (Which pages and path exactly and where inside the files)
Tried this post as well: Opencart get product downloads
But it is not exactly working on product page (product.php)
Opencart Version 3.0.2.0

Answer 1

Ok I'll take a stab at this but let's clarify a few things:
1) DB_PREFIX is simply a php constant that's declared in your config.php file. Based on the query you provided it's probably equal to ocuk. The point is, you write queries using this constant and they become portable across installations regardless of the users' chosen database prefix.
2) Opencart is based on the MCVL (an extension of MVC which includes language files) structure. The place to execute queries is in the model. The place to call model methods is in the controller. The controller passes output to the view and often uses language variables from language files.
So what I would do is write function and put it in your product model – in this case that's catalog/model/catalog/product.php. This function is called a method since it's now part of your model class. The function will output the rows in your table that a logged in customer has purchased the given product. It's also important to check (a) that the customer is logged in and (b) that the orders you are querying against are real orders - with an order_status_id > 0. We can go into that but suffice to say that you always need to check the order_status_id if you want to know about actual completed orders. Such a method could look something like this:
public function getOrderProductHistory($product_id) {
$result = [];
if ($customer_id = $this->customer->getId()) {
$sql = "
SELECT *
FROM " . DB_PREFIX . "order o
JOIN " . DB_PREFIX . "order_product op USING (order_id)
WHERE o.order_status_id > 0
AND o.customer_id = '" . (int)$customer_id . "'
";
$query = $this->db->query($sql);
$result = $query->rows;
}
return $result;
}
Now in your controller (on a product page that's catalog/controller/product/product.php) you can call this method to get results like this:
$order_product_history = $this->model_catalog_product->getOrderProductHistory($product_id);
And then do something based on the output:
if ($order_product_history) {
$data['has_been_ordered'] = true;
} else {
$data['has_been_ordered'] = false;
}
Now $has_been_ordered is a boolean that you can access in your view to display a message to the customer. There's still a bit more code for you to write but hopefully this helps get you off to a good start.