13.2.1.1. The application logic

Example 13-1 is the application logic that produces the order receipt. The script logic is identical to that of the shipping.2 script discussed in Chapter 12. The different features of this script are the omission of any code to produce output, and the inclusion of the fragments of code that assign database values to presentation elements, parse these elements, and call functions in the template class library.

The script in Example 13-1 works as follows:

1. Include the xtpl.p template library.

2. In the function show_HTML_receipt( ), associate the script with the template shown in Example 13-2:

   $xtpl= new XTemplate ("example.shipping.3.xtpl");

   This creates a new template object called $xtpl.

3. Query the customer table and assign the returned $row to an element of the template named CUSTOMER. Also assign the orderID session variable to an element of the template named ORDER_ID. Uppercase strings are used to distinguish template elements from variables in the script, but this isn't essential. After assigning the data, parse the main.customer template data (we discuss the structure of the template later in this section).

4. Retrieve and assign each item in the order to the template elements QTY, WINE, PRICE, and TOTAL. Now check that this data is correctly formed and associated by parsing it. The following lines perform these functions:

   // Assign the qty, wine details, price, and total item
   // cost to the template
   $xtpl->assign("QTY", $row["qty"]);
   $xtpl->assign("WINE", $wineDetail);      
   $xtpl->assign("PRICE", sprintf("%-.2f", $row["price"]));     
   $xtpl->assign("TOTAL", sprintf("%-.2f", $itemsPrice));  
   
   // Parse a template row of items
   $xtpl->parse("main.items.row");

   We explain how this relates to the template later.

5. Assign the overall order total to the template and check the overall structure of the data. The final check includes parsing the items and the overall main output, and then outputting the data with the following code:

   $xtpl->assign("ORDER_TOTAL",
   sprintf("%-.2f", $orderTotalPrice));
   
   // parse all items
   $xtpl->parse("main.items");
   
   // parse the whole document
   $xtpl->parse("main");
   
   // output the templated data
   $xtpl->out("main");

13.2.1.2. The template

Example 13-2 is the template itself. It consists mostly of HTML but also contains a Cascading Style Sheet for presentation. Cascading Style Sheets (CSS) are used to control the styles that present output; references that discuss the CSS standard are listed in Appendix E.

Interleaved throughout the template are the following HTML comments:

<!-- BEGIN: main -->
  <!-- BEGIN: customer -->
  <!-- END: customer -->
  <!-- BEGIN: items -->
    <!-- BEGIN: row -->
    <!-- END: row -->
  <!-- END: items -->
<!-- END: main -->

These comments describe the structural elements referenced in the PHP script in Example 13-1. The elements are nested, so that the element customer is a child of main, because <!-- BEGIN: customer --> occurs inside the <!-- BEGIN: main --> and <!-- END: main --> tags. The customer element can therefore be referenced in Example 13-1 as main.customer. A table row can be referenced in Example 13-1 as main.items.row, because the structural element row is inside items, and items is inside main.

Consider now how the template produces row data:

<!-- BEGIN: row -->
<tr>
  <td>{QTY}</td>
  <td>{WINE}</td>
  <td align="right">$ {PRICE}</td>
  <td align="right">$ {TOTAL}</td>
</tr>
<!-- END: row -->

The tags {QTY}, {WINE}, {PRICE}, and {TOTAL} represent where data is inserted. The data is assigned to these tags in Example 13-1 using the assign( ) function. For example, {QTY} is the position where the order item quantities from the database appear. If there are two database rows assigned to main.items.row elements, two <tr> rows are produced as the body of the HTML <table>.

The customer details are output by accessing the CUSTOMER element. For example, the shipping details are produced with the fragment:

<p>If it existed, the order would have been shipped to: 
<br><b>
{CUSTOMER.title} {CUSTOMER.firstname} {CUSTOMER.initial}
{CUSTOMER.surname}
<br>
{CUSTOMER.addressline1}
{CUSTOMER.addressline2}
{CUSTOMER.addressline3}
<br>{CUSTOMER.city} {CUSTOMER.state} {CUSTOMER.zipcode}
<br>{CUSTOMER.country}
</b>

The overall result of running Example 13-1 and using the template in Example 13-2 is the output in Figure 13-1. The advantage of this approach is that the HTML in Example 13-2 can be altered independently of the script in Example 13-1 and vice versa. This means that application logic and presentation are as separate as possible. The only links between the two are the structural markup components and the embedded tags.

Figure 13-1. Output of Examples 13-1 and 13-2

The XTemplate library has more complex features not discussed here. More details on the use of templates can be found at the web sites listed earlier in this section.