Suggestions for Shopping Cart class

[RyanMinor]

I know there are many open source shopping carts available, but I wanted to write my own to gain a better understanding of the coding practices involved. Below is my almost finished shopping cart class for an e-commerce website I am building. I want to be able to handle all purchasing capability from the Cart class as you can see from what I have below. I was wondering if anyone can see any areas for improvement before I go implementing it into my website. Any help is appreciated and thank you in advance.

 

<?php

/**
* Cart class handles all shopping cart activity.
* 
* This class also handles saving order information for each purchase.
* 
* After each order is complete be sure to call the Product::inventoryCheck() 
* to notify administrator of low quantities.
*/

class Cart
{
public $db;
private $_cartName;

/**
 * Creates a new shopping cart if one does not exist already.
 * Initiates the database connection for future use.
 */
public function __construct($cartName = 'cart') {
	$this->_cartName = $cartName;
	if (!isset($_SESSION[$this->_cartName])) {
		$_SESSION[$this->_cartName];
	}
	$this->db = Database::getInstance();
}

/**
 * Returns all items in the shopping cart and their information.
 * I want to be able to return the quantity as well.
 * I will take this information and use it to display the shopping cart to the customer.
 */
public function getCartItems() {
	try {
		foreach ($_SESSION[$this->_cartName][$id] as $productId => $quantity) {
			$stmt = $this->db->prepare(
				"SELECT 
					product_id, 
					product_name, 
					product_thumb, 
					product_price, 
					product_discount
				FROM product 
				WHERE product_id = ?");
			$stmt->setFetchMode(PDO::FETCH_ASSOC);
			$stmt->execute(array($productId));
			return array($stmt->fetchAll(), $quantity);
		}
	} catch (Exception $e) {
		return FALSE;
	}
}

/**
 * Adds an item to the shopping cart.
 * Also used to change quantities of items already in shopping cart.
 * @param $id - integer
 * @param $quantity - integer ($quantity comes from a drop down menu populated by the database)
 */
public function addItem($id, $quantity) {
	try {
		$_SESSION[$this->_cartName][$id] = $quantity;
	} catch (Exception $e) {
		return FALSE;
	}
}

/**
 * Deletes an item from the shopping cart.
 * @param $id - integer
 */
public function deleteItem($id) {
	try {
		unset($_SESSION[$this->_cartName][$id]);	
	} catch (Exception $e) {
		return FALSE;
	}
}

	/**
 * Empties all contents out of the shopping cart.
 * Call this function when all purchase activity is complete so the user has a new cart to start with.
 */
public function clearCart() {
	try {
		unset($_SESSION[$this->_cartName]);
	} catch (Exception $e) {
		return FALSE;
	}
}

/**
 * Saves a purchase after it is successful.
 * @param $subTotal - integer
 * @param $tax - integer
 * @param $discount - integer
 * @param $total - integer
 */
public function savePurchase($subTotal, $tax, $discount, $total) {
	try {
		$stmt = $this->db->prepare(
			"INSERT INTO purchase
				(purchase_customer_id, 
				purchase_timestamp, 
				purchase_ip, 
				purchase_subtotal, 
				purchase_tax, 
				purchase_discount, 
				purchase_total, 
				purchase_status)
			VALUES 
				(?, ?, ?, ?, ?, ?, ?, ?)");
		$stmt->execute(array($_SESSION['customer_id'], NOW(), $_SERVER['REMOTE_ADDR'], $subTotal, 
		$tax, $discount, $total));
		return $purchaseId;
	} catch (Exception $e) {
		return FALSE;
	}
}

/**
 * Saves each item from a purchase.
 * Updates product quantities in product table.
 * @param $purchaseId - integer
 */
public function saveCartItems($purchaseId) {
	try {
		foreach ($_SESSION[$this->_cartName][$id] as $productId => $quantity) {
			$stmt = $this->db->prepare(
				"INSERT INTO purchase_item
					(purchase_item_product_id, 
					purchase_item_purchase_id, 
					purchase_item_quantity)
				VALUES 
					(?, ?)");
			$stmt->execute(array($productId, $purchaseId, $quantity));
			$update = $this->db->prepare(
				"UPDATE product
				SET product_quantity = product_quantity - $quantity
				WHERE product_id = ?");
			$update->execute(array($productId));
		}			
	} catch (Exception $e) {
		return FALSE;
	}
}

/**
 * Calculates shipping cost and applies it to the shopping cart.
 */
public function shipping() {
	// need to find out pricing structure
}

/**
 * Applies a coupon discount if coupon parameters are met
 * Checks for coupon code validity from the coupon table
 * @param $couponCode - varchar
 */
public function useCoupon($couponCode, $cartPrice) {
	try {
		$stmt = $this->db->prepare(
			"SELECT coupon_amount, coupon_minimum_price
			FROM coupon
			WHERE coupon_code = ? AND coupon_active = 'Yes'");
		$stmt->setFetchMode(PDO::FETCH_ASSOC);
		$stmt->execute(array($couponCode));
		$stmt->fetch();
		// make sure there is a coupon available that matches customer input
		if (count($stmt) != 1) {
			return FALSE;
		}
		// chcek if the current cart price (minus taxes and shipping) is greater than coupon minimum price
		if ($cartPrice < $stmt['coupon_minimum_price']) {
			return FALSE;
		}
		// this will go in the coupon field in the cart view
		return $stmt['coupon_amount'];
	} catch (Exception $e) {
		return FALSE;
	}
}

}

[the182guy]

I would split this up to handle checkout/purchase code into a checkout class and just keep cart relate stuff in the cart class.

[RyanMinor]

I would split this up to handle checkout/purchase code into a checkout class and just keep cart relate stuff in the cart class.

 

I was considering that as well. I think I will do that.