Question

I have a cart class, where I store the product ids. The user can open the cart through a button that opens the cart in a popup, so the cart content has to be loaded in every page.

I can store only the ids of the products because of the size limits, but I want to show the product names to the final user, so for each element I need to make a query and get the product data from the database.

Is there any major drawback by doing this? Or are there better solutions?

PS: I could get the id of all the products in the cart, and then do one single query that gets the data of any needed product. I’d rather avoid this since I would need to rewrite parts of the class, so is there any actual difference with the previous solution?

PPS: The total number of sql queries shouldn’t be too high in any case. Of course I wouldn’t mind, but I strongly doubt any user will purchase hundreds of different products at one time.

Answer 1

I only like to highlight one sentence from your question:

so for each element I need to make a query and get the product data from the database.

That is your problem. You do not need to do that. You can query your database with a single query and ask for all products that are in a list of IDs.

A helpful part of the SQL language is the IN(....) clause.

$ids = [123, 884, 7848, 2882, 3232]; // let's say that is your input
$idList = implode(',', array_map('intval', $ids));
$sql = sprintf(
    "SELECT field1, field2, field3 FROM products WHERE products.ID IN(%s)",
    $idList
);

This is a single query for a list of product IDs. When you fetch the data from the data-base you create a in-memory-database on the fly (aka Hashtable) so that you can “fetch” data based on ID:

foreach($ids as $id)
{
    $concreteProduct = $rows[$id];
    ...
}

You also know it as array, just keyed by the ID value returned from the database. As the ID is unique, this just works^tm.

Hope this is helpful. Some might it call premature optimization, however, you should be aware of the concept, because this can be used in many cases.