Open the index.php file in the product_manager directory and add an action that displays the Category List page. Then, t

[answerhappygod]

Open the index.php file in the product_manager directory and addan action that displays the Category List page. Then, test this tomake sure it works correctly. At this point, the page should onlydisplay some of the headings.
<?phprequire('../model/database.php');require('../model/product_db.php');require('../model/category_db.php');
$action = filter_input(INPUT_POST, 'action');if ($action == NULL) { $action = filter_input(INPUT_GET, 'action'); if ($action == NULL) { $action = 'list_products'; }}
if ($action == 'list_products') { $category_id = filter_input(INPUT_GET,'category_id', FILTER_VALIDATE_INT); if ($category_id == NULL || $category_id == FALSE){ $category_id = 1; } $category_name =get_category_name($category_id); $categories = get_categories(); $products =get_products_by_category($category_id); include('product_list.php');} else if ($action == 'delete_product') { $product_id = filter_input(INPUT_POST,'product_id', FILTER_VALIDATE_INT); $category_id = filter_input(INPUT_POST,'category_id', FILTER_VALIDATE_INT); if ($category_id == NULL || $category_id == FALSE|| $product_id == NULL ||$product_id == FALSE) { $error = "Missing or incorrect productid or category id."; include('../errors/error.php'); } else { delete_product($product_id); header("Location:.?category_id=$category_id"); }} else if ($action == 'show_add_form') { $categories = get_categories(); include('product_add.php'); } else if ($action == 'add_product') { $category_id = filter_input(INPUT_POST,'category_id', FILTER_VALIDATE_INT); $code = filter_input(INPUT_POST, 'code'); $name = filter_input(INPUT_POST, 'name'); $price = filter_input(INPUT_POST, 'price'); if ($category_id == NULL || $category_id == FALSE ||$code == NULL || $name == NULL || $price== NULL || $price == FALSE) { $error = "Invalid product data. Checkall fields and try again."; include('../errors/error.php'); } else { add_product($category_id, $code, $name,$price); header("Location:.?category_id=$category_id"); }} ?>