Notice: Undefined variable: product_title in C:\xampp\htdocs\e-commerce\cart.php on line 335

enter image description here

<div class="cart_section">
    <div class="container">
        <div class="row">
            <div class="col-lg-10 offset-lg-1">
                <div class="cart_container">
                    <div class="cart_title">Shopping Cart</div>
                    <div class="cart_items">
                        <ul class="cart_list">
                            <li class="cart_item clearfix">
                                <div class="cart_item_image"><img src="admin_area/product_images/<?php echo $product_image;?>" alt=""></div>

what is the wrong here when i test page find that error