Beginning PHP and MySQL E-Commerce From Novice to Professional phần 6 doc

Execute the following code, which creates the catalog_get_categories stored procedure in your tshirtshop database; catalog_get_categories simply returns all the categories from your cata

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■ Note A complete description of the $_FILESsuperglobal is available at http://www.php.net/manual/

As you can see, it’s pretty simple to handle file uploads with PHP

Product Details: Implementing the Business Tier

To implement the business tier, you’ll need to add the following methods to the Catalog class:

• UpdateProduct updates a product’s details: name, description, price, and discountedprice

• DeleteProduct completely removes a product from the catalog

• RemoveProductFromCategory is called when the “Remove from category” button isclicked to unassign the product from a category

• GetCategories returns all the categories from our catalog

• GetProductInfo returns the product details

• GetCategoriesForProduct is used to get the list of categories that are related to the ified product

spec-• SetProductDisplayOption sets the product’s display setting

• AssignProductToCategory assigns a product to a category

• MoveProductToCategory moves a product from one category to another

• GetAttributesNotAssignedToProduct returns all the attribute values from the table ofattribute_valuesthat have not been assigned to a product.

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• AssignAttributeValueToProduct assigns an attribute value to a product.

• RemoveProductAttributeValue removes the association between a product and anattribute value from the product_attribute table

• SetImage1 changes the image file name in the database for a certain product

• SetImage2 changes the second image file name in the database for a certain product

• SetThumbnail changes the thumbnail image file name for a certain product

Exercise: Implementing the Business Tier Methods

Because the functionality is better expressed by the data tier functions that the methods call, we’ll discuss them

in more detail when we implement the data tier For now, simply add the following code to the Catalog class, inbusiness/catalog.php:

// Updates a product

public static function UpdateProduct($productId, $productName,

$productDescription, $productPrice,

$productDiscountedPrice){

// Build the SQL query

$sql = 'CALL catalog_update_product(:product_id, :product_name,

:product_description, :product_price,:product_discounted_price)';

// Build the parameters array

$params = array (':product_id' => $productId,

':product_name' => $productName,':product_description' => $productDescription,':product_price' => $productPrice,

':product_discounted_price' => $productDiscountedPrice);// Execute the query

DatabaseHandler::Execute($sql, $params);

}// Removes a product from the product catalog

public static function DeleteProduct($productId){

// Build SQL query

$sql = 'CALL catalog_delete_product(:product_id)';

$params = array (':product_id' => $productId);

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// Execute the queryDatabaseHandler::Execute($sql, $params);

}// Unassigns a product from a category

public static function RemoveProductFromCategory($productId, $categoryId){

// Build SQL query

$sql = 'CALL catalog_remove_product_from_category(

:product_id, :category_id)';

':category_id' => $categoryId);

// Execute the query and return the resultsreturn DatabaseHandler::GetOne($sql, $params);

}// Retrieves the list of categories a product belongs to

public static function GetCategories()

{// Build SQL query

$sql = 'CALL catalog_get_categories()';

// Execute the query and return the resultsreturn DatabaseHandler::GetAll($sql);

}// Retrieves product info

public static function GetProductInfo($productId){

// Build SQL query

$sql = 'CALL catalog_get_product_info(:product_id)';

// Execute the query and return the resultsreturn DatabaseHandler::GetRow($sql, $params);

}// Retrieves the list of categories a product belongs to

public static function GetCategoriesForProduct($productId){

// Build SQL query

$sql = 'CALL catalog_get_categories_for_product(:product_id)';

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// Execute the query and return the resultsreturn DatabaseHandler::GetAll($sql, $params);

}// Assigns a product to a category

public static function SetProductDisplayOption($productId, $display){

// Build SQL query

$sql = 'CALL catalog_set_product_display_option(

:product_id, :display)';

':display' => $display);

}// Assigns a product to a category

public static function AssignProductToCategory($productId, $categoryId){

// Build SQL query

$sql = 'CALL catalog_assign_product_to_category(

:product_id, :category_id)';

':category_id' => $categoryId);

}// Moves a product from one category to another

public static function MoveProductToCategory($productId, $sourceCategoryId,

$targetCategoryId){

// Build SQL query

$sql = 'CALL catalog_move_product_to_category(:product_id,

:source_category_id, :target_category_id)';

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':source_category_id' => $sourceCategoryId,':target_category_id' => $targetCategoryId);

}// Gets the catalog attributes that are not assigned to the specified product

public static function GetAttributesNotAssignedToProduct($productId){

// Build the SQL query

$sql = 'CALL catalog_get_attributes_not_assigned_to_product(:product_id)';

}// Assign an attribute value to the specified product

public static function AssignAttributeValueToProduct($productId,

$attributeValueId){

// Build SQL query

$sql = 'CALL catalog_assign_attribute_value_to_product(

:product_id, :attribute_value_id)';

':attribute_value_id' => $attributeValueId);

}// Removes a product attribute value

public static function RemoveProductAttributeValue($productId,

$attributeValueId){

// Build SQL query

$sql = 'CALL catalog_remove_product_attribute_value(

:product_id, :attribute_value_id)';

':attribute_value_id' => $attributeValueId);

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}// Changes the name of the product image file in the database

public static function SetImage($productId, $imageName){

// Build SQL query

$sql = 'CALL catalog_set_image(:product_id, :image_name)';

$params = array (':product_id' => $productId, ':image_name' => $imageName);// Execute the query

}// Changes the name of the second product image file in the database

public static function SetImage2($productId, $imageName){

// Build SQL query

$sql = 'CALL catalog_set_image_2(:product_id, :image_name)';

$params = array (':product_id' => $productId, ':image_name' => $imageName);// Execute the query

}// Changes the name of the product thumbnail file in the database

public static function SetThumbnail($productId, $thumbnailName){

// Build SQL query

$sql = 'CALL catalog_set_thumbnail(:product_id, :thumbnail_name)';

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Product Details: Implementing the Data Tier

In the data tier, you add the stored procedures that correspond to the business tier methods in

the Catalog class you have just seen

Exercise: Adding the Stored Procedures

1 Use phpMyAdmin to execute and create the stored procedures described in the following steps, and don’t

forget to set $$ as the delimiter before executing the code

2 Execute the following code, which creates the catalog_update_product stored procedure to your

tshirtshop database The catalog_update_product stored procedure updates the details of

a product using the data received through the inProductId, inName, inDescription, inPrice, andinDiscountedPrice input parameters

Create catalog_update_product stored procedureCREATE PROCEDURE catalog_update_product(IN inProductId INT,

IN inName VARCHAR(100), IN inDescription VARCHAR(1000),

IN inPrice DECIMAL(10, 2), IN inDiscountedPrice DECIMAL(10, 2))BEGIN

UPDATE productSET name = inName, description = inDescription, price = inPrice,discounted_price = inDiscountedPrice

WHERE product_id = inProductId;

END$$

3 Execute the following code, which creates the catalog_delete_product stored procedure to your

tshirtshop database The catalog_delete_product stored procedure completely removes a productfrom the catalog by deleting its entries in the product_attribute, product_category, and producttables

Create catalog_delete_product stored procedureCREATE PROCEDURE catalog_delete_product(IN inProductId INT)BEGIN

DELETE FROM product_attribute WHERE product_id = inProductId;

DELETE FROM product_category WHERE product_id = inProductId;

DELETE FROM product WHERE product_id = inProductId;

END$$

4 Execute the following code, which creates the catalog_remove_product_from_category stored

procedure in your tshirtshop database The catalog_remove_product_from_category stored cedure verifies how many categories the product exists in If the product exists in more than one category, itjust removes the product from the specified category (ID received as a parameter) If the product is associ-ated with a single category, it is removed completely from the database

pro - Create catalog_remove_product_from_category stored procedureCREATE PROCEDURE catalog_remove_product_from_category(

IN inProductId INT, IN inCategoryId INT)

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BEGINDECLARE productCategoryRowsCount INT;

SELECT count(*)FROM product_categoryWHERE product_id = inProductIdINTO productCategoryRowsCount;

IF productCategoryRowsCount = 1 THENCALL catalog_delete_product(inProductId);

SELECT 0;

ELSEDELETE FROM product_categoryWHERE category_id = inCategoryId AND product_id = inProductId;

SELECT 1;

END IF;

END$$

5 Execute the following code, which creates the catalog_get_categories stored procedure in your

tshirtshop database; catalog_get_categories simply returns all the categories from your catalog. Create catalog_get_categories stored procedure

CREATE PROCEDURE catalog_get_categories()BEGIN

SELECT category_id, name, descriptionFROM category

ORDER BY category_id;

END$$

6 Execute the following code, which creates the catalog_get_product_info stored procedure in your

tshirtshop database The catalog_get_product_info stored procedure retrieves the product name,description, price, discounted price, image, the second image, thumbnail, and display option for the productidentified by the product ID (inProductId)

Create catalog_get_product_info stored procedureCREATE PROCEDURE catalog_get_product_info(IN inProductId INT)BEGIN

SELECT product_id, name, description, price, discounted_price,image, image_2, thumbnail, display

FROM productWHERE product_id = inProductId;

END$$

7 Execute this code, which creates the catalog_get_categories_for_product stored procedure in

your tshirtshop database The catalog_get_categories_for_product stored procedure returns

a list of the categories that belong to the specified product Only their IDs and names are returned, becausethis is the only information we’re interested in

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Create catalog_get_categories_for_product stored procedureCREATE PROCEDURE catalog_get_categories_for_product(IN inProductId INT)BEGIN

SELECT c.category_id, c.department_id, c.nameFROM category c

JOIN product_category pc

ON c.category_id = pc.category_idWHERE pc.product_id = inProductId

9 Execute the following code, which creates the catalog_assign_product_to_category stored

proce-dure in your tshirtshop database The catalog_assign_product_to_category stored proceproce-dureassociates a product with a category by adding a (product_id, category_id) value pair into the product_

10 Execute the following code, which creates the catalog_assign_product_to_category stored

proce-dure in your tshirtshop database The catalog_move_product_to_category stored proceproce-dureremoves a product from a category and places it in another one

Create catalog_move_product_to_category stored procedureCREATE PROCEDURE catalog_move_product_to_category(IN inProductId INT,

IN inSourceCategoryId INT, IN inTargetCategoryId INT)BEGIN

UPDATE product_categorySET category_id = inTargetCategoryIdWHERE product_id = inProductId

AND category_id = inSourceCategoryId;

END$$

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11 Execute the following code, which creates the catalog_get_attributes_not_assigned_to_product

stored procedure in your tshirtshop database This procedure returns all attribute values that weren’talready associated with the product in the product_attribute table

Create catalog_get_attributes_not_assigned_to_product stored procedureCREATE PROCEDURE catalog_get_attributes_not_assigned_to_product(

IN inProductId INT)BEGIN

SELECT a.name AS attribute_name,

av.attribute_value_id, av.value AS attribute_valueFROM attribute_value av

INNER JOIN attribute a

ON av.attribute_id = a.attribute_idWHERE av.attribute_value_id NOT IN

(SELECT attribute_value_idFROM product_attributeWHERE product_id = inProductId)ORDER BY attribute_name, av.attribute_value_id;

END$$

12 Execute the following code, which creates the catalog_assign_attribute_value_to_product

stored procedure in your tshirtshop database This procedure assigns an attribute value to a product byadding a new record to the product_attribute table

Create catalog_assign_attribute_value_to_product stored procedureCREATE PROCEDURE catalog_assign_attribute_value_to_product(

IN inProductId INT, IN inAttributeValueId INT)BEGIN

INSERT INTO product_attribute (product_id, attribute_value_id)VALUES (inProductId, inAttributeValueId);

END$$

13 Execute the following code, which creates the catalog_remove_product_attribute_value stored

procedure in your tshirtshop database This procedure unassigns an attribute value from a product bydeleting the necessary record from the product_attribute table

Create catalog_remove_product_attribute_value stored procedureCREATE PROCEDURE catalog_remove_product_attribute_value(

IN inProductId INT, IN inAttributeValueId INT)BEGIN

DELETE FROM product_attributeWHERE product_id = inProductId AND

attribute_value_id = inAttributeValueId;

END$$

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14 Execute this code, which creates the catalog_set_image, catalog_set_image_2, and catalog_set_

thumbnail stored procedures into your tshirtshop database We need these functions to change theprimary, secondary and/or thumbnail image of a product when uploading a new picture

Create catalog_set_image stored procedureCREATE PROCEDURE catalog_set_image(

IN inProductId INT, IN inImage VARCHAR(150))BEGIN

UPDATE product SET image = inImage WHERE product_id = inProductId;

END$$

15 Load your product details page, and ensure everything works the way it should You have a lot of

functional-ity to test! Figures 11-4 and 11-5 show the product details admin page in action

How It Works: Administering Product Details

No administrative feature is fun to implement, but what you’ve accomplished so far is quite impressive Your shop

administrators can now edit a product’s name, description, and price; delete products from the database or from

just a category; assign a product to one or more categories; and manage product attributes and pictures

At this moment you’re offering all the important features that are necessary to administer a web site like TShirtShop

We will, however, add yet another feature that will make the life of our shop administrators much easier: in-store

administration links

Creating In-Store Administration Links

Right now, the administration page delivers all the important requirements: administrators can

manage the catalog departments, categories, products, and their attributes In the last part of

this chapter, we implement an additional feature, which makes the administrator’s task a little

bit easier This feature consists of Edit buttons, such as the Edit Department Details and Edit

Product Details buttons you can see in Figure 11-6 These buttons show up only if the visitor is

authenticated as an administrator and take him or her directly to the item administrative page

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Figure 11-6. Edit Department Details and Edit Product Details buttons in TShirtShop

Exercise: Implementing In-Store Administration Links

1 Open the tshirtshop.css file from the styles folder, and add the following style definitions:

div.yui-b div form.edit-form{

margin: 0;

padding: 0;

}.edit-form{

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<p class="description">{$obj->mDescription}</p>

{if $obj->mShowEditButton}

<form action="{$obj->mEditActionTarget}" method="post" class="edit-form">

<input type="submit" name="submit_{$obj->mEditAction}"

value="{$obj->mEditButtonCaption}" />

</form>

{/if}

{include file="products_list.tpl"}

3 Add the following highlighted members to the Department class in presentation/department.php:

// Deals with retrieving department detailsclass Department

{// Public variables for the smarty templatepublic $mName;

4 Also in presentation/department.php, add the following piece of code at the end of the constructor of

the Department class This makes the Edit button show up if the user is an administrator

/* If CategoryId is in the query string we save it (casting it to integer to protect against invalid values) */

$category_details =Catalog::GetCategoryDetails($this->_mCategoryId);

$this->mName = $this->mName ' » '

$category_details['name'];

$this->mDescription = $category_details['description'];

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$this->mEditActionTarget = Link::ToDepartmentCategoriesAdmin($this->_mDepartmentId);

$this->mEditAction = 'edit_cat_' $this->_mCategoryId;

$this->mEditButtonCaption = 'Edit Category Details';

}

else {

$this->mEditActionTarget = Link::ToDepartmentsAdmin();

$this->mEditAction = 'edit_dept_' $this->_mDepartmentId;

$this->mEditButtonCaption = 'Edit Department Details';

}

}}

?>

6 Add the following piece of code to presentation/templates/product.tpl:

{* Add the submit button and close the form *}

7 Add these members to the Product class in presentation/product.php:

// Handles product detailsclass Product

{// Public variables to be used in Smarty templatepublic $mProduct;

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8 Add this code at the end of the constructor of the Product class, in presentation/product.php This

code ensures the Edit button shows up only if the user is an administrator:

elsetrigger_error('ProductId not set');

// Show Edit button for administrators

9 In the same file, add the highlighted piece of code at the end of the init() method of the Product class.

This creates the link to the edit product administration page

// Build links for product departments and categories pagesfor ($i = 0; $i < count($this->mLocations); $i++)

{

$this->mLocations[$i]['link_to_department'] =Link::ToDepartment($this->mLocations[$i]['department_id']);

$this->mLocations[$i]['link_to_category'] =Link::ToCategory($this->mLocations[$i]['department_id'],

$this->mLocations[$i]['category_id']);

}

// Prepare the Edit button

$this->mEditActionTarget = Link::Build(str_replace(VIRTUAL_LOCATION, '', getenv('REQUEST_URI')));

if (isset ($_SESSION['admin_logged']) &&

$_SESSION['admin_logged'] == true &&

isset ($_POST['submit_edit'])) {

$product_locations = $this->mLocations;

if (count($product_locations) > 0) {

$department_id = $product_locations[0]['department_id'];

$category_id = $product_locations[0]['category_id'];

header('Location: ' htmlspecialchars_decode(

Link::ToProductAdmin($department_id,

$category_id,

$this->_mProductId)));

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} }

}}

?>

10 Add the following piece of code to presentation/templates/products_list.tpl This adds the Edit

buttons to the product lists

{* Add the submit button and close the form *}

11 Open presentation/products_list.php, and add the following members to the ProductsList class:

public $mAllWords = 'off';

public $mSearchString;

public $mEditActionTarget;

public $mShowEditButton;

// Private membersprivate $_mDepartmentId;

private $_mCategoryId;

12 Add the following piece of code to the end of the construct() method of the ProductsList class:

if ($this->mPage < 1)trigger_error('Incorrect Page value');

// Save page request for continue shopping functionality

$_SESSION['link_to_continue_shopping'] = $_SERVER['QUERY_STRING'];

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// Show Edit button for administrators

13 Also in presentation/products_list.php, add the following piece of code at the beginning of the

init() method of ProductsList:

public function init(){

// Prepare the Edit button

$this->mEditActionTarget = Link::Build(str_replace(VIRTUAL_LOCATION, '', getenv('REQUEST_URI')));

if (isset ($_SESSION['admin_logged']) &&

$_SESSION['admin_logged'] == true &&

isset ($_POST['product_id'])) {

if (isset ($this->_mDepartmentId) && isset ($this->_mCategoryId)) header('Location: '

htmlspecialchars_decode(

Link::ToProductAdmin($this->_mDepartmentId,

$this->_mCategoryId, (int)$_POST['product_id'])));

else {

$product_locations = Catalog::GetProductLocations((int)$_POST['product_id']);

if (count($product_locations) > 0) {

$department_id = $product_locations[0]['department_id'];

$category_id = $product_locations[0]['category_id'];

header('Location: ' htmlspecialchars_decode(

Link::ToProductAdmin($department_id,

$category_id, (int)$_POST['product_id'])));

} } }

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/* If searching the catalog, get the list of products by callingthe Search business tier method */

if (isset ($this->mSearchString)){

// Get search results

$search_results = Catalog::Search($this->mSearchString,

$this->mAllWords,

$this->mPage,

$this->mrTotalPages);

14 Open presentation/store_front.php, and add the following piece of code at the beginning of the

init() method of the StoreFront class:

public function init(){

$_SESSION['link_to_store_front'] = Link::Build(str_replace(VIRTUAL_LOCATION, '', getenv('REQUEST_URI')));

// Create "Continue Shopping" link for the PayPal shopping cart

if (!isset ($_GET['AddProduct'])){

15 Open presentation/admin_menu.php, and modify the constructor of the AdminMenu class like this:

public function construct(){

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Figure 11-7. Administering product details

How It Works: In-Store Administration Links

In this exercise, we created Edit buttons throughout the product catalog that are displayed only when the current

user is logged in as an administrator This way, an administrator who notices, say, a product description that needs

to be updated can click the Edit button for that product right from the catalog, rather than having to browse the

administration pages to find that product

Implementing this feature wasn’t probably the most exciting coding exercise you’ve ever completed, but it’s a really

useful feature that your clients will certainly appreciate!

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In this chapter, you implemented the administrative features for your products, includingfeatures for adding or editing product attributes, assigning products to categories, uploadingproduct pictures, and so on You’ve also updated TShirtShop to include edit buttons in thecatalog pages, so administrators can much more easily access the administration pages forupdating the catalog information

Now that the dry part of developing the administration end of our site is finished, we arefinally ready to move on the really exciting features In Chapter 12, you’ll implement your ownshopping cart in TShirtShop, replacing the PayPal shopping cart you’ve been using so far

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Phase II

of Development

P A R T 2

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Creating Your Own

Shopping Cart

Welcome to the second stage of development! During this stage, you’ll start improving and

adding new features to the already existing, fully functional e-commerce site

So, what exactly can you improve? Well, the answer to this question isn’t hard to find if youtake a quick look at the popular e-commerce sites on the Web They personalize the experi-

ence for the user, provide product recommendations, remember customers’ preferences, and

boast many other features that make the site easy to remember and hard to leave without first

purchasing something

In the first stage of development, you extensively relied on a third-party payment processor(PayPal) that supplied an integrated shopping cart, so you didn’t record any shopping cart or

order information in the database Right now, your site isn’t capable of displaying a list of “most

wanted” products or any other information about the products that have been sold through

the web site because, at this stage, you aren’t tracking the products sold Saving order information

in the database is one of our priorities now because most of the features you want to implement

next rely on having this information

At the end of this chapter you’ll have a functional shopping cart, but the visitor will notyet be able to order the products contained in it You’ll add this functionality in Chapter 14,

when you implement a custom checkout system that integrates with your new shopping cart

Specifically, in this chapter you’ll learn how to

• Analyze the elements of a shopping cart

• Create the database structure that stores shopping cart records

• Implement the data tier, business tier, and presentation tier components of theshopping cart

• Update the PayPal Add to Cart buttons you created in Chapter 9 to work with the newshopping cart

• Create a shopping cart summary box to remind users of the products in their carts and

of the total amounts

• Implement a shopping cart administration page that allows site administrators todelete shopping carts that weren’t updated in a specified number of days

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Designing the Shopping Cart

In this chapter we will implement a custom shopping cart, which stores data in the localtshirtshopdatabase This will provide you with much more flexibility than the PayPal shoppingcart, over which you have no control and which cannot be easily saved into your database forfurther processing and analysis With the custom shopping cart, when the visitor clicks the Add

to Cart button for a product, the product is still added to the visitor’s shopping cart, but this cartand product information will be stored directly in the tshirtshop database rather than the inac-cessible PayPal database When the visitor clicks the View Cart button, a page like the one shown

in Figure 12-1 appears

Figure 12-1. The TShirtShop shopping cart

Our shopping cart will have a “Save for later” feature, which allows the visitor to orderonly a subset of the products in the cart and save the other items for purchase at a later time.When a product is saved for later, it’s moved to a separate list of the shopping cart and is notincluded in the order when the visitor checks out (see Figure 12-2)

In all the other pages except the shopping cart page, the visitor will be able to see a ping cart summary in the left part of the screen, as shown in Figure 12-3

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Figure 12-2. The TShirtShop “Save for later” feature

Figure 12-3. The TShirtShop shopping cart summary

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Before starting to write the code for the shopping cart, let’s take a closer look at what we’regoing to do.

First, note that you won’t have any user personalization features at this stage of the site

It doesn’t matter who buys your products at this point; you just want to know what productswere sold and when When you add user customization features in the later chapters, yourtask will be fairly simple: when the visitor authenticates, the visitor’s temporary (anonymous)shopping cart will be associated with the visitor’s account Because you work with temporaryshopping carts, even after implementing the customer account system, the visitor isn’t required

to supply additional information (log in) earlier than necessary

We use cookies to keep track of shopping carts When the visitor clicks the Add to Cartbutton, the server first verifies whether a shopping cart cookie already exists on the visitor’scomputer If it does, the specified product is added to the existing cart Otherwise, the servergenerates a unique cart ID, saves it to the client’s cookie, and then adds the product to thenewly generated shopping cart

Storing Shopping Cart Information

You will store all the information from the shopping carts in a single table named

shopping_cart Follow the next exercise to create the shopping_cart table

Exercise: Creating the shopping_cart Table

1 Load phpMyAdmin, select your tshirtshop database, and open a new SQL query page.

2 Execute the following code, which creates the shopping_cart table in your tshirtshop database:

Create shopping_cart tableCREATE TABLE `shopping_cart` (

`item_id` INT NOT NULL AUTO_INCREMENT,

`cart_id` CHAR(32) NOT NULL,

`product_id` INT NOT NULL,

`attributes` VARCHAR(1000) NOT NULL,

`quantity` INT NOT NULL,

`buy_now` BOOL NOT NULL DEFAULT true,

`added_on` DATETIME NOT NULL,PRIMARY KEY (`item_id`),

KEY `idx_shopping_cart_cart_id` (`cart_id`));

How It Works: The shopping_cart Table

Let’s look at each field in shopping_cart:

• item_id is the primary key of the table Its value uniquely identifies a shopping cart record

• cart_id is a CHAR(32) value that uniquely identifies a visitor’s shopping cart (as opposed to just oneshopping cart record)

• product_id references the ID of an existing product

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• attributes is a varying character field that stores the attributes that were selected by the visitor whenadding the product to the shopping cart A possible value of this field can be, for example, "Color/Size:

White/XL"

• quantity stores the product quantity in the shopping cart

• buy_now is a Boolean field with the default value of true that supports the “Save for later” feature Whenthe customer checks out, only the products that have this value set to true are added to the order, whereasthe “Save for later” products remain in the shopping cart

• added_on is a date field that is populated with the date the product was added to the cart This value isused to calculate the age of a shopping cart, which gives us the ability to delete old shopping carts from thedatabase

The value of the first field, item_id, is calculated every time a new record is created in the table No surprises

here—you have worked with AUTO_INCREMENT columns before

The value of cart_id represents the ID of the shopping cart This value is calculated by the business tier each

time a new shopping cart is created The cart_id field contains a value that uniquely identifies a visitor’s

shop-ping cart

It’s important to understand that a visitor can have several products in the shopping cart, that each product can

have different attribute configurations, and that a customer can purchase the same product several times, each

with different attributes For example, a visitor can have a Black/L Torch t-shirt and a Pink/M Torch t-shirt in the

cart For this reason, the only combination of fields that guarantees the uniqueness of the cart items is (cart_id,product_id, attributes), which could serve as the table primary key

But wait! MySQL has a limitation regarding the size of the columns that form a primary key Trying to create the

primary key as specified earlier triggers the following error: “#1071 – Specified key was too long; max key length

is 999 bytes.” What the error basically says is that the cumulated size of the columns forming the primary key

cannot exceed 999 bytes, and in our case the three fields exceed 3,000 bytes (a UT8-encoded character takes

three bytes) This means that if you want to create the primary key of the three fields, you’d have to limit the size

of attributes to 269 characters This limitation may or may not be acceptable to you, depending on what you’re

selling, and even if it is OK today, you might need larger attributes tomorrow!

Our workaround is to create an artificial primary key value—item_id—and then use that field as the primary

key This solution of adding a new field breaks the rules of the third normal form, or simply said, it’s not a perfect

database design; however, with some careful planning, it allows us to implement a functional shopping cart

Implementing the Data Tier

Now we’ll create the stored procedures that support the necessary shopping cart operations

We’ll create these procedures in the tshirtshop database:

• shopping_cart_add_product adds a product to the shopping cart

• shopping_cart_update modifies shopping cart products’ quantities and subsequentpricing

• shopping_cart_remove_product deletes a product from the visitor’s shopping cart

• shopping_cart_get_products gets the list of products in the specified shopping cart and

is called when you want to show the user the shopping cart

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• shopping_cart_get_saved_products gets the list of products saved to buy later and iscalled when the user requests the shopping cart details page.

• shopping_cart_get_total_amount returns the total costs of the products in the specifiedproduct cart

• shopping_cart_save_product_for_later saves a product to a shopping cart for laterpurchase

• shopping_cart_move_product_to_cart moves a product from the “Save for later” listback to the “main” shopping cart

Now let’s create each method one at a time in the following exercise

Exercise: Implementing the Stored Procedures

1 Use phpMyAdmin to create the stored procedures described in the following steps Don’t forget to set the

$$ delimiter before executing the code of each step

2 Create the shopping_cart_add_product stored procedure in your tshirtshop database by executing

DECLARE productQuantity INT;

Obtain current shopping cart quantity for the productSELECT quantity

FROM shopping_cartWHERE cart_id = inCartIdAND product_id = inProductIdAND attributes = inAttributesINTO productQuantity;

Create new shopping cart record, or increase quantity of existing record

IF productQuantity IS NULL THENINSERT INTO shopping_cart(cart_id, product_id, attributes,

quantity, added_on)VALUES (inCartId, inProductId, inAttributes, 1, NOW());

ELSEUPDATE shopping_cartSET quantity = quantity + 1, buy_now = trueWHERE cart_id = inCartId

AND product_id = inProductIdAND attributes = inAttributes;

END IF;

END$$

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The shopping_cart_add_product stored procedure is called when the visitor clicks the Add to Cartbutton for one of the products If the selected product already exists in the shopping cart, its quantity isincreased by one; otherwise, one new unit is added to the shopping cart (a new shopping_cart record iscreated).

The procedure receives three parameters: inCartId, inProductId, and inAttributes It first mines whether the product already exists in the shopping cart by looking for cart_id, product_id, andattributes If this combination exists in the shopping_cart table, it means the visitor already has theproduct in its shopping cart, so you update the existing quantity by adding one unit Otherwise, shopping_

deter-cart_add_product creates a new record for the product in shopping_cart with a default quantity of 1

The NOW() MySQL function is used to retrieve the current date to populate the added_on field

3 Execute the following code, which creates the shopping_cart_update stored procedure in your

tshirtshop database:

Create shopping_cart_update_product stored procedureCREATE PROCEDURE shopping_cart_update(IN inItemId INT, IN inQuantity INT)BEGIN

IF inQuantity > 0 THENUPDATE shopping_cartSET quantity = inQuantity, added_on = NOW()WHERE item_id = inItemId;

ELSECALL shopping_cart_remove_product(inItemId);

END IF;

END$$

The shopping_cart_update stored procedure updates the quantity of one item This stored procedure iscalled when the visitor clicks the Update button in the shopping cart page and is called once for each itemthat needs to be updated

The procedure receives two parameters: inItemId and inQuantity If inQuantity is zero or less,shopping_cart_update is smart enough to remove the mentioned item from the shopping cart Other-wise, it updates the quantity of the item in the shopping cart and also updates added_on to accuratelyreflect the time the record was last modified Updating added_on is useful for the catalog administrationpage, where this field is used to calculate the shopping cart age and remove old shopping carts For thispurpose, we consider that an item whose quantity has been modified is a “new item.”

4 Execute the following code, which creates the shopping_cart_remove_product stored procedure in

your tshirtshop database:

Create shopping_cart_remove_product stored procedureCREATE PROCEDURE shopping_cart_remove_product(IN inItemId INT)BEGIN

DELETE FROM shopping_cart WHERE item_id = inItemId;

END$$

The shopping_cart_remove_product stored procedure removes an item from the shopping cart when

a visitor clicks the Remove button for one of the items in the shopping cart

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5 Execute this code, which creates the shopping_cart_get_products stored procedure in your

Create shopping_cart_get_products stored procedureCREATE PROCEDURE shopping_cart_get_products(IN inCartId CHAR(32))BEGIN

SELECT sc.item_id, p.name, sc.attributes,

COALESCE(NULLIF(p.discounted_price, 0), p.price) AS price,sc.quantity,

END$$

The shopping_cart_get_products stored procedure returns the items in the shopping cart mentioned

by the inCartId parameter Because the shopping_cart table stores the product_id for each product

it stores, you need to join the shopping_cart and product tables to get the information you need.Note that some of the items can have discounted prices When an item has a discounted price (which hap-pens when its discounted_price value is different from 0), then its discounted price should be used forcalculations Otherwise, its list price should be used The following expression returns discounted_price

if different from 0; otherwise, it returns price

COALESCE(NULLIF(p.discounted_price, 0), p.price)

■ Note This is the first time you’ve worked with the COALESCEand NULLIFconditional expressions, so we’llnow explain what they do.COALESCEcan receive any number of parameters, and it returns the first one that

is not NULL.NULLIFreceives two parameters and returns NULLif they’re equal; otherwise, it returns the first

of the parameters In our case, we use NULLIFto test whether the p.discounted_priceis 0; if this tion is true,NULLIFreturns false, and the COALESCEfunction will return p.price If p.discounted_price

condi-is different from 0, the whole expression returns p.discounted_price

6 Execute the following code, which creates the shopping_cart_get_saved_products stored procedure

in your tshirtshop database:

Create shopping_cart_get_saved_products stored procedureCREATE PROCEDURE shopping_cart_get_saved_products(IN inCartId CHAR(32))BEGIN

SELECT sc.item_id, p.name, sc.attributes,

COALESCE(NULLIF(p.discounted_price, 0), p.price) AS priceFROM shopping_cart sc

INNER JOIN product p

ON sc.product_id = p.product_idWHERE sc.cart_id = inCartId AND NOT sc.buy_now;

END$$

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The shopping_cart_get_saved_products stored procedure returns the items saved for later in theshopping cart specified by the inCartId parameter.

7 Execute the following code, which creates the shopping_cart_get_total_amount stored procedure in

your tshirtshop database:

Create shopping_cart_get_total_amount stored procedureCREATE PROCEDURE shopping_cart_get_total_amount(IN inCartId CHAR(32))BEGIN

SELECT SUM(COALESCE(NULLIF(p.discounted_price, 0), p.price)

* sc.quantity) AS total_amountFROM shopping_cart sc

INNER JOIN product p

ON sc.product_id = p.product_idWHERE sc.cart_id = inCartId AND sc.buy_now;

END$$

The shopping_cart_get_total_amount stored procedure returns the total value of the items in theshopping cart before applicable taxes and shipping charges This is called when displaying the total amountfor the shopping cart If the cart is empty, total_amount will be 0

8 Execute the following code, which creates the shopping_cart_save_product_for_later stored

pro-cedure in your tshirtshop database:

Create shopping_cart_save_product_for_later stored procedureCREATE PROCEDURE shopping_cart_save_product_for_later(IN inItemId INT)BEGIN

UPDATE shopping_cartSET buy_now = false, quantity = 1WHERE item_id = inItemId;

END$$

The shopping_cart_save_product_for_later stored procedure saves a shopping cart item to the

“Save for later” list so the visitor can buy it later (the item isn’t sent to checkout when placing the order)

This is accomplished by setting the value of the buy_now field to false

9 Execute this code, which creates the shopping_cart_move_product_to_cart stored procedure in your

Create shopping_cart_move_product_to_cart stored procedureCREATE PROCEDURE shopping_cart_move_product_to_cart(IN inItemId INT)BEGIN

UPDATE shopping_cartSET buy_now = true, added_on = NOW()WHERE item_id = inItemId;

END$$

The shopping_cart_move_product_to_cart stored procedure sets the buy_now state for a shoppingcart item to true, so the visitor can buy the product when placing the order

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Implementing the Business Tier

To implement the business tier for the shopping cart, we’ll create a file named shopping_cart.php,which contains the ShoppingCart class This class has the following methods:

• SetCartId() generates a new shopping cart ID and saves it on the visitor’s browser as

a cookie and in the session

• GetCartId() returns the shopping cart ID

• AddProduct() adds a new product to the visitor’s shopping cart

• Update() modifies a product quantity in the visitor’s shopping cart or deletes the productfrom the cart if the quantity is zero or negative

• RemoveProduct() removes a product from the shopping cart

• GetCartProducts() retrieves all the products in the shopping cart

• GetTotalAmount() returns the total amount of the products in the cart

• SaveProductForLater() saves a product in the cart for later

• MoveProductToCart() moves a product from the “Save for later” list back to the “main”shopping cart

Let’s write the code

Exercise: Implementing the Shopping Cart Business Logic

1 First, add the following two lines at the end of your include/config.php file These constants are used

to differentiate between current shopping cart items and items that are saved for later

// Shopping cart item typesdefine('GET_CART_PRODUCTS', 1);

define('GET_CART_SAVED_PRODUCTS', 2);

2 Create a new file called shopping_cart.php in the business folder Add the following code to the file,

and then we’ll comment on it afterward:

<?php// Business tier class for the shopping cart

class ShoppingCart

{// Stores the visitor's Cart IDprivate static $_mCartId;

// Private constructor to prevent direct creation of object

private function construct(){

}

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/* This will be called by GetCartId to ensure we have thevisitor's cart ID in the visitor's session in case

$_mCartID has no value set */

public static function SetCartId(){

// If the cart ID hasn't already been set

if (self::$_mCartId == ''){

// If the visitor's cart ID is in the session, get it from there

if (isset ($_SESSION['cart_id'])){

self::$_mCartId = $_SESSION['cart_id'];

}// If not, check whether the cart ID was saved as a cookieelseif (isset ($_COOKIE['cart_id']))

{// Save the cart ID from the cookieself::$_mCartId = $_COOKIE['cart_id'];

$_SESSION['cart_id'] = self::$_mCartId;

// Regenerate cookie to be valid for 7 days (604800 seconds)setcookie('cart_id', self::$_mCartId, time() + 604800);

}else{/* Generate cart id and save it to the $_mCartId class member,the session and a cookie (on subsequent requests $_mCartIdwill be populated from the session) */

self::$_mCartId = md5(uniqid(rand(), true));

// Store cart id in session

// Cookie will be valid for 7 days (604800 seconds)setcookie('cart_id', self::$_mCartId, time() + 604800);

}}}// Returns the current visitor's card id

public static function GetCartId()

{// Ensure we have a cart id for the current visitor

if (!isset (self::$_mCartId))self::SetCartId();

return self::$_mCartId;

}

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// Adds product to the shopping cart

public static function AddProduct($productId, $attributes){

// Build SQL query

$sql = 'CALL shopping_cart_add_product(

:cart_id, :product_id, :attributes)';

$params = array (':cart_id' => self::GetCartId(),

':product_id' => $productId,':attributes' => $attributes);

}// Updates the shopping cart with new product quantities

public static function Update($itemId, $quantity){

// Build SQL query

$sql = 'CALL shopping_cart_update(:item_id, :quantity)';

$params = array (':item_id' => $itemId,

':quantity' => $quantity);

}// Removes product from shopping cart

public static function RemoveProduct($itemId){

// Build SQL query

$sql = 'CALL shopping_cart_remove_product(:item_id)';

$params = array (':item_id' => $itemId);

}// Gets shopping cart products

public static function GetCartProducts($cartProductsType){

$sql = '';

// If retrieving "active" shopping cart products

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if ($cartProductsType == GET_CART_PRODUCTS){

// Build SQL query

$sql = 'CALL shopping_cart_get_products(:cart_id)';

}// If retrieving products saved for later

elseif ($cartProductsType == GET_CART_SAVED_PRODUCTS){

// Build SQL query

$sql = 'CALL shopping_cart_get_saved_products(:cart_id)';

}elsetrigger_error($cartProductsType ' value unknown', E_USER_ERROR);

$params = array (':cart_id' => self::GetCartId());

}/* Gets total amount of shopping cart products before tax and/orshipping charges (not including the ones that are beingsaved for later) */

public static function GetTotalAmount(){

// Build SQL query

$sql = 'CALL shopping_cart_get_total_amount(:cart_id)';

$params = array (':cart_id' => self::GetCartId());

// Execute the query and return the resultsreturn DatabaseHandler::GetOne($sql, $params);

}// Save product to the Save for Later list

public static function SaveProductForLater($itemId){

// Build SQL query

$sql = 'CALL shopping_cart_save_product_for_later(:item_id)';

}

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// Get product from the Save for Later list back to the cart

public static function MoveProductToCart($itemId){

// Build SQL query

$sql = 'CALL shopping_cart_move_product_to_cart(:item_id)';

}}

?>

3 Include a reference to shopping_cart.php in index.php:

// Load Business Tierrequire_once BUSINESS_DIR 'catalog.php';

require_once BUSINESS_DIR 'shopping_cart.php';

How It Works: The Business Tier of the Shopping Cart

When a visitor adds a product or requests any shopping cart operation, we generate a shopping cart ID for the visitor

if there isn’t one You take care of this in the SetCartId() method that generates a cart ID to the $_mCartId ber of the ShoppingCart class The shopping cart ID is also saved in the visitor’s session and in a persistent cookie.SetCartId() starts by verifying that the $_mCartId member was already set, in which case we don’t need toread it from external sources:

mem-public static function SetCartId(){

// If the cart ID hasn't already been set

if (self::$_mCartId == ''){

If we don’t have the ID in the member variable, the next place to look is the visitor’s session:

// If the visitor's cart ID is in the session, get it from there

if (isset ($_SESSION['cart_id'])){

self::$_mCartId = $_SESSION['cart_id'];

}

If the ID couldn’t be found in the session either, we check whether it was saved as a cookie If yes, we save thevalue both to the session and to the $_mCartId member, and we regenerate the cookie to reset its expiration date:// If not, check whether the cart ID was saved as a cookie

elseif (isset ($_COOKIE['cart_id'])){

// Save the cart ID from the cookie

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member, and to the persistent cookie:

else{/* Generate cart id and save it to the $_mCartId class member,the session and a cookie (on subsequent requests $_mCartIdwill be populated from the session) */

self::$_mCartId = md5(uniqid(rand(), true));

// Store cart id in session

// Cookie will be valid for 7 days (604800 seconds)setcookie('cart_id', self::$_mCartId, time() + 604800);

}}}Three functions are used to generate the cart ID: md5(), uniqid(), and rand() The call to md5(uniqid(rand(),

true)) generates a unique, difficult-to-predict, 32-byte value, which represents the cart ID

■ Note If you’re interested to know the details about generating the cart ID, here they are The md5()

function uses the Message-Digest algorithm 5 (MD5) to calculate the hash value of a value it receives as

a parameter The hash value is 32 characters long The uniqid()function returns a unique identifier based

on the current time in microseconds; its first parameter is the prefix to be appended to its generated value,

in this case, the rand()function that returns a pseudo-random value between 0and RAND_MAX, which is

platform dependent If the second parameter of uniqid()is true,uniqid()adds an additional combined

linear congruential generator (combined LCG) entropy at the end of the return value, which should make the

results even “more unique.”

In short, uniquid(rand(), true) generates a “very unique” value, which is passed through md5() to ensure

that it becomes a random sequence of characters that is 32 characters long

The SetCartId method is used only by the GetCartId() method that returns the cart ID GetCartId() first

checks to see whether $_mCartId has been set, and if not, it calls SetCartId() before returning the value of

$_mCartId:

// Returns the current visitor's cart idpublic static function GetCartId()

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