add_item_cart.php

<?php 
session_start();

// Returning an error if an account is not logged in
if (!isset($_SESSION['id'])) {
  // Go back to the store page
  // Get the referer URL
  $referer = $_SERVER['HTTP_REFERER'];
  
  // Check if the referer has the "product_id" parameter
  if (strpos($referer, 'product_id=') !== false) {
    // If the "product_id" parameter is present, preserve only the "product_id" parameter
    $refererParts = parse_url($referer);
    $newReferer = $refererParts['scheme'] . '://' . $refererParts['host'] . $refererParts['path'] . '?product_id=' . $_GET['product_id'] ;
  } else {
    // If the "product_id" parameter is not present, remove all existing parameters
    $newReferer = $referer;
  }
  
  // Add success parameter to the URL
  $newReferer .= (strpos($newReferer, '?') === false ? '?' : '&') . 'error=Sign in or Create an Account to add items to your wishlist';
  
  // Redirect to the new URL
  header('Location: ' . $newReferer);
  exit();
  }
    
// Removing the item from the user's cart
$id = $_SESSION['id'];
$productID = $_GET['product_id'];

require_once 'db_conn.php';

$sql = "INSERT INTO cart_items (product_id, user_id, quantity) VALUES ($productID, $id, 1)";
mysqli_query($conn, $sql);

//Add the item to the sesion cart
$_SESSION['cart'][] = $productID;

// Remove the item from the user's wishlist
$sql = "DELETE FROM wish_list_items WHERE product_id = '$productID' AND user_id = '$id'";
mysqli_query($conn, $sql);

//Remove the item from the session wishlist
$index = array_search($productID, $_SESSION['wishlist']);
unset($_SESSION['wishlist'][$index]);

// Go back to the store page
// Get the referer URL
$referer = $_SERVER['HTTP_REFERER'];

// Check if the referer has the "product_id" parameter
if (strpos($referer, 'product_id=') !== false) {
  // If the "product_id" parameter is present, preserve only the "product_id" parameter
  $refererParts = parse_url($referer);
  $newReferer = $refererParts['scheme'] . '://' . $refererParts['host'] . $refererParts['path'] . '?product_id=' . $_GET['product_id'];
} else {
  // If the "product_id" parameter is not present, remove all existing parameters
  $newReferer = $referer;
}

// Add success parameter to the URL
$newReferer .= (strpos($newReferer, '?') === false ? '?' : '&') . 'success=Your item has been added to the cart';

// Redirect to the new URL
header('Location: ' . $newReferer);
exit();

?>