Hello all, I am creating my first shopping cart in cakephp but got stuck while updating the product quantity. I want to update the product quantity using a session variable. Problem here is that when ever I am adding the same product to the cart it is added as a new item to the list but what I want is the quantity counter should increment to 1 when I select the product that I have already selected. I am using cakephp version 2.8.1. Can anybody help me with the code?

Here is my Cart.ctp code:

<?php
/* display message saved in session if any */
echo $this->Session->flash();
?>

<h2 style="text-align:center;color:white">Cart</h2>
<div>
    <?php 
      //link to products page
      echo $this->Html->link('Back To Product List', array('action' => 'product')); 
    ?>
</div>
<table align="center">
    <tr>
        <th>Name</th>
        <th>Price</th>
        <th>Action</th>
    </tr>
    <?php $totalPrice = 0; ?>
    <?php foreach ($cart as $key => $product): ?>
    <tr>
        <td>
            <?php 
              //link to product page
              echo $this->Html->link($product['Product']['product_id'], array('action'=> 'view', $product['Product']['id'])); 
            ?>
        </td>
        <td>
            <?php 
              //show product price
              echo $product['Product']['product_price']; 
            ?>
        </td>
        <td>
            <?php 
              //remove product from a cart
              echo $this->Html->link('delete', array('action' => 'delete',$key)); 
            ?>
        </td>
    </tr>
    <?php 
    //calculate total price of all products in a cart
    $totalPrice = $totalPrice + $product['Product']['product_price']; 
    ?>
<?php endforeach; ?>
    <tr>
        <th>Total Price: </th>
        <th><?php 
          //show total price
           echo $totalPrice; 
           ?>
        </th>
        <th>
          <?php
            //delete all elements from a cart
            echo $this->Html->link('empty', array('controller'=>'users','action'=>'empty_cart'));
          ?>
        </th>
    </tr>
</table>

UserController code:

public function product(){
        //find all products
        $products = $this->Product->find('all');
        //set counter to display number of products in a cart
        $counter = 0;
        if ($this->Session->read('Counter')) {
            $counter = $this->Session->read('Counter');
        }
        //pass variable to view
        $this->set(compact('products', 'counter'));

    }
    function cart($id=null)
     {
        $this->Product->id = $id;
        if(!$this->Product->exists())
        {
            throw new NotFoundException(__('Invalid product'));
        }
        $productsInCart = $this->Session->read('Cart');
        //pr($productsInCart);die;

        $amount=count($productsInCart);  
        $this->Session->write('Cart.' . $amount, $this->Product->read(null, $id));  
      
        //pr($ans);die;
        $this->Session->write('Counter', $amount + 1);
        $this->Session->setFlash(__('Product added to cart'));

        $this->redirect('showcart');
      }function showcart()
     {
        $cart = array();

        if ($this->Session->check('Cart')) {
            $cart = $this->Session->read('Cart');
        }

        $this->set(compact('cart'));
    }

Any help will be appreciated. Thanks in advance.