cart_update.php

<?php
session_start(); //start session
require_once (__DIR__.'/scripts/config.php');

//add product to session or create new one
if(isset($_POST["type"]) && $_POST["type"]=='add' && $_POST["product_qty"]>0)
{
    foreach($_POST as $key => $value){ //add all post vars to new_product array
        $new_product[$key] = filter_var($value, FILTER_SANITIZE_STRING);
    }
    //remove unecessary vars
    unset($new_product['type']);
    unset($new_product['return_url']); 
    
    $code=$new_product['product_code'];
    echo $code;
    
    //we need to get product name and price from database.
    $sql="Select itemDescription,itemPrice from item where itemID=$code";
    $qrystmt=$DB_con->prepare($sql);
    $qrystmt->execute();
    
    while($row=$qrystmt->fetchObject()){
        
        //fetch product name, price from db and add to new_product array
        $new_product["product_name"] = $row->itemDescription; 
        $new_product["product_price"] = $row->itemPrice;
        
        if(isset($_SESSION["cart_products"])){  //if session var already exist
            if(isset($_SESSION["cart_products"][$new_product['product_code']])) //check item exist in products array
            {
                unset($_SESSION["cart_products"][$new_product['product_code']]); //unset old array item
            }           
        }
        $_SESSION["cart_products"][$new_product['product_code']] = $new_product; //update or create product session with new item  
    } 
}


//update or remove items 
if(isset($_POST["product_qty"]) || isset($_POST["remove_code"]))
{
    //update item quantity in product session
    if(isset($_POST["product_qty"]) && is_array($_POST["product_qty"])){
        foreach($_POST["product_qty"] as $key => $value){
            if(is_numeric($value)){
                $_SESSION["cart_products"][$key]["product_qty"] = $value;
            }
        }
    }
    //remove an item from product session
    if(isset($_POST["remove_code"]) && is_array($_POST["remove_code"])){
        foreach($_POST["remove_code"] as $key){
            unset($_SESSION["cart_products"][$key]);
        }   
    }
}

//back to return url
$return_url = (isset($_POST["return_url"]))?urldecode($_POST["return_url"]):''; //return url
header('Location:'.$return_url);