compare a single field from an object array - php

Question

I'm revamping the packaging screen in our inventory system. The user opens a package and inserts/removes the items in it, and when he presses Save, a json array of all the parts that are in the package is sent to a PHP endpoint which takes care of saving the package in the database.
So far everything is good, I have created my functions to send data between PHP and javascript. However, even though the json array that javascript sends to PHP contains all the info on the products (as javascript needed to retrieve it anyway to fill in the grid in the gui), I still have to validate everything in PHP because I can't be sure that the user didn't tampered with the data from the console before trying to save.
With that said, in PHP, I receive the json array, which I use the IDs to load a list of proper objects into an array. I'm doing this:
$in = str_repeat('?,', count($itemIDs) - 1) . '?';
$sql = "SELECT * FROM tbProduct WHERE nID IN ($in)";
$sttmt = $db->prepare($sql);
$sttmt->execute($itemIDs);
$res = $sttmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($res as $key => $productInfo) {
$prod = new tbProduct($db);
$prod->loadFromArray($productInfo);
}
so far so good, I now have an array of tbProduct, which is my class for the products.
What I now have to do is run a validation on this array of objects to make sure all these objets are in the proper status to be packaged together. These validations include making sure all the products have the same status, that none of the products are assembly parts, that all the products have the same owner, etc. This way, even if the array was tampered with in the browser's console, I'll be sure to use the information from the DB anyway.
So I need a way to validate this. I could just do a foreach, store everything that needs to be checked from the very first item in variables, and just compare each subsequent item to these variables, but I'm sure there are better ways to do this. I need something that will be as efficient as possible. My packages can(and will) contain several hundreds of products, so the solution needs to be fast.
What would be the best way of doing this?
Thank you!

Answer 1

You can do it during the loop that's processing all the data returned by the query. Set a variable to the first object, then you can compare other elements to it.
$res = $sttmt->fetchAll(PDO::FETCH_ASSOC);
$firstprod = new tbProduct($db);
$firstprod->loadFromArray(array_shift($res));
foreach ($res as $key => $productInfo) {
$prod = new tbProduct($db);
$prod->loadFromArray($productInfo);
if ($prod->status != $firstprod->status) {
// report inconsistent status
} elseif ($prod->owner != $firstprod->owner) {
// report inconsistent owner
} elseif ($prod->type != "assembly") {
// report that it must ba an assembly part
} ...
}