Looping through multi-dimensional array to pre-populate dynamically generated form - php

Question

I am trying to create an ecommerce site. I have products that have different attributes (e.g. colour) and each of these needs to have their own model number and price etc,.
I have generated a form to gather this information and save it. However, I want to be able to save this info as a $_SESSION variable while users are adding products, so that they can come back to the price section and the form will be pre-populated with what they previously entered even though they haven't actually saved the product to the DB yet.
To do this I have a string that I treat as an array of items stored as a $_SESSION variable in PHP in the following format:
'item-test,100,20,20,20,20,£,1,item-test,100,20,20,20,20,£,2'
I parse this into an actual array I can deal with like so (when it gets to actually saving the product my SQL query is inside this foreach() loop):
if(isset($_SESSION['price_array'])){
$price_array = $_SESSION['price_array'];
$result = explode("item-",$price_array);
foreach($result as $item){
if(isset($item) && $item!=""){
$itemValue = explode(",",$item);
$product_model_no = $itemValue[0];
$product_value = $itemValue[1];
$product_discount = $itemValue[2];
$product_margin = $itemValue[3];
$product_shipping_domestic = $itemValue[4];
$product_shipping_other = $itemValue[5];
$product_currency = $itemValue[6];
$product_attribute = $itemValue[7];
}
}
}
So to generate this form I've another loop that goes through all of the possible attributes (not all products might come in all colours so only the ones stored in the $_SESSION apply). If I try to pre-populate this as it is my variables above only have the values for the last item in the array.
However if I nest this inside the other loop it will get the correct data but it will generate the form a number of times depending on how many items are in the array, with each iteration of the form having the values for that item in the array.
I know this is very convoluted to try explain and I can't really provide all my code because it is very complex and most of it is generated in PHP from other information in other locations.
Edit
The basics of how the form is being generated inside the other loop is as follows:
$params = [$attribute];
$sql = "SELECT * FROM attributes WHERE id=?";
$attributeResult = DB::run($sql,$params);
foreach ($attributeResult as $value) {
for ($i = 1; $i <= 15; $i++) {
//generate form here
if($i == $product_attribute){
// pre-populate form here
}
}
}