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Chapter 11. The Winestore Shopping Cart

In this chapter, we introduce the shopping cart developed for the online winestore. The shopping cart is typical of those used in online stores: the user can add items to the cart and manage the quantities of the different items. The solution we outline is scalable and practical. The cart data is stored in the winestore database tables, and only one session variable per user is required to track the cart's identity.

This chapter is the second of four that outline the complete winestore application. As discussed in Chapter 10, the descriptions of the scripts aren't comprehensive, and we assume you've read Chapter 2 to Chapter 9 as background. Also, we encourage you to install a local copy of the application and to view, edit, and use the scripts while reading this chapter.

We present here the four scripts that manage the shopping cart, a fifth script that produces the home page that includes the Hot New Wines panel, and a sixth script that manages redirection to other pages when the user clicks on buttons.

The scripts in this chapter perform the following functions:

Present the home page
Display the Hot New Wines panel based on the examples developed in Chapter 4 and Chapter 5

View the shopping cart
Query the database and display the contents of the user's shopping cart

Add items to the cart
Add a quantity of a specific wine to the user's shopping cart

Empty the cart
Delete all the items in the cart and remove the cart

Update quantities
Manage changes to the number of bottles of wines in the cart, including deletion of one or more wines

Process button clicks and redirect the browser
Manage the redirections required when the user presses the different buttons on each of the winestore pages

As with the other modules in the winestore, the shopping cart isn't a production system. The scripts presented here illustrate the practice of developing a web database application. Techniques shown include database interactivity, concurrency management, using sessions, and one- and two-component querying.

11.1. The Winestore Home Page

Example 11-1 shows the final implementation of the winestore home page containing the Hot New Wines panel. The Hot New Wines panel is discussed in more detail in Chapter 4, and the one-component functionality for adding one or a dozen bottles of wine to the cart is discussed in Chapter 5. We discuss how clicks on the add-to-cart links are managed later in Section 11.2.

The Hot New Wines panel is based on scripts presented in Chapter 4 and is encapsulated in the function showPanel( ) in Example 11-1. The functions showVarieties( ), which displays the varieties of a specific wine, and showPricing( ), which shows the per-bottle and the per-case price of a wine, are part of the include.inc file discussed in Chapter 10.

The main body of the script presents the front page using a mixture of HTML and calls to functions. The function showCart( ) displays an embedded link cart icon and the dollar total and number of items in the cart. The function showMessage( ) displays any message registered in the session variable message, and the showLogin( ) function displays the user's login status. The function loginButtons( ) shows the user different buttons depending on whether or not she is currently logged in. All these functions are part of include.inc and discussed in Chapter 10.

The following code fragment inserts the file disclaimer into the body of the HTML:

require 'disclaimer';

The file is a text message that alerts the user that our system doesn't really sell wines and that the scripts are covered by the GNU public license.

Example 11-1. cart.1 displays the winestore home page

   // This is the script that shows the user a list of
   // wines, and allows them to select wines to add to
   // their shopping cart
   include 'include.inc';


   function showPanel($query, $connection)
      // Run the query on the database through
      // the connection
      if (!($result = @ mysql_query ($query, $connection)))
         showerror( );

      echo "<table border=0>\n";

      // Process the three new wines
      while ($row = @ mysql_fetch_array($result)) 
         // Begin a heading for the wine
         echo "<tr>\n\t<td bgcolor=\"maroon\">" .
              "<b><font color=\"white\">" . 
              $row["year"] . " " .
              $row["winery_name"] . " " .
              $row["wine_name"] . " ";

         // Print the varieties for this wine
         echo showVarieties($connection, $row["wine_id"]);     

         // Finish the first row heading
         echo "</font></b></td>\n</tr>\n";

         // Print the wine review
         if (!empty($row["description"]))
            echo "<tr>\n\t<td bgcolor=\"silver\">" .
                 "<b>Review: </b>" .
         // Print the pricing information
         echo "<tr>\n\t<td bgcolor=\"gray\">";

         // Print out the pricing information
         showPricing($connection, $row["wine_id"]);

         echo "</td>\n</tr>\n";

         // Show the single-bottle add to cart link
         echo "<tr>\n\t<td align=\"right\">" .
              "<a href=\"example.cart.3.php?" .
              "qty=1&amp;wineId=" .
              $row["wine_id"] .
              "\">Add a bottle to the cart</a>";  

         // Show the dozen add to cart link
         echo "&nbsp;&nbsp;&nbsp;" .
      "<a href=\"example.cart.3.php?qty=12&amp;wineId=" .
      $row["wine_id"] . "\">Add a dozen</a></td>\n";  

         echo "</tr>\n";

         // Blank row for presentation
         echo "\n<tr>\n\t<td></td>\n</tr>\n";

      echo "</table>\n";

   // ---------
   // Initialize a session. This call either creates 
   // a new session or re-establishes an existing one. 
   session_start( );    

   // Open a connection to the DBMS
   if (!($connection = @ mysql_connect($hostName, 
      showerror( );

   if (!mysql_select_db($databaseName, $connection))
      showerror( );
  "-//W3C//DTD HTML 4.01 Transitional//EN"
    <title>Hugh and Dave's Online Wines</title>
<body bgcolor="white">
   // Show the user login status
   showLogin( );

   // Show the dollar and item total of the cart
   <h1>Here are some Hot New Wines!</h1>
   // Display any messages to the user
   showMessage( );

   // Show the "Hot New Wines"
   $query = "SELECT wi.winery_name, 
             FROM wine w, winery wi, inventory i
             WHERE w.winery_id = wi.winery_id
             AND w.wine_id = i.wine_id
             AND w.description IS NOT NULL 
             GROUP BY w.wine_id
             ORDER BY i.date_added DESC LIMIT 3";

   // Include our disclaimer
   require 'disclaimer';

   // Show the user the "Hot New Wines" panel
   showPanel($query, $connection);

   echo "<form action=\"example.cart.5.php\"" .
        " method=\"GET\">\n";
   echo "<table>\n<tr>\n";

   // If the cart has contents, offer the opportunity 
   // to view the cart or empty the cart. 
   if (session_is_registered("order_no"))
      echo "\t<td><input type=\"submit\" " .
           "name=\"empty\" value=\"Empty Cart\"></td>\n";
      echo "\t<td><input type=\"submit\" " .
           "name=\"view\" value=\"View Cart\"></td>\n";

   // Show the user the search screen button
   echo "\t<td><input type=\"submit\" " .
        "name=\"search\" value=\"Search\"></td>\n";

   // Show the user either a login or logout button
   loginButtons( );

   echo "\n</tr>\n</table>\n";
   echo "</form>\n";

<br><a href="http://validator.w3.org/check/referer">
    <img src="http://www.w3.org/Icons/valid-html401"
    height="31" width="88"
    align="right" border="0" alt="Valid HTML 4.01!"></a>

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