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IT 280 Web Development II, Spring 2008

Dynamic pages with PHP - part 2

The problem

One big problem facing web sites is maintenance--the need to keep the content up to date and expand the site.
It is impossible to code every page from scratch for large sites and almost impossible for many smaller ones.
One solution is to design the pages in such as way that many parts are basically the same from page to page
With this approach, only the key content part varies.

Templates

A template is a pattern for a page with one or more "blanks" where the different content is filled in.
Carefully designed templates make it possible to generate site pages automatically.
A site may use more than one template.

Template Technique

The template is saved in one file
the different content parts are saved in separate files. (They might also be stored in a database.)

Using PHP include

The content files must be included - merged into prpper places the template.
The PHP include function provides one way to assemble pages.
Other techniques include Server Side Includes (SSI), ASP includes, custom server-side programming in Perl, Java, or another language, and specialized web server languages such as Cold Fusion .

Using the QUERY_STRING

The include function needs information about which content is to be included in the template.
For this example, we provide it in the query string.
The query string is written at the end of the URL, following a question mark.
```
http://wyrd.hood.edu/third.php?hello_world
```
It is accessed in a program using the variable
```
$_SERVER["QUERY_STRING"]
```

Example

Template page

<html>
<head>
 <title>breaking it up with PHP</title>
</head>

<body>
<h1>A demo of one way to assemble sites with PHP</h1> 

<?php
    $which =  $_SERVER["QUERY_STRING"];
    //The query string is the name of the content file to be included

    if ( $which == "") { 
    // If there wasn't any content file name, give the home page
        include "home.php";
        }
    else {
    // Otherwise include the file whose name was provided 
        include $which;
        } 
?>    

<hr />
<p>Footer Footer Footer Footer Footer </p>
</body>
</html>

Content page

The three content files are very short. They only contain the part that is different from page to page.

In this example they have been given the .php file extension, although it isn't necessary.

The file home.php

<h1>Welcome to PHP includes demo</h1> 

<p>This is the home page</p>

<?php
  echo "How are you today?" ?>

The file second_page.php

<h1>Continued PHP includes demo</h1> 

<p>This is the second page.  its content is inserted into the 
framework of the template.  It is a very powerful technique for 
making a site easier to update.</p>

The file third_page.php

<h1>PHP includes demo continued some more</h1> 

<p>This is the third page.<br />The file contains only 
two lines of content, the part that is different from the other pages.  
The displayed page is a lot larger.</p>

Adding links to the pages

This version of the example adds a set of navigation links. Now the beginning is.

<html>
<head>
 <title>breaking it up with PHP</title>
</head>

<body>
<a href="main2.php?home.php">HOME PAGE</a> |
  <a href="main2.php?second_page.php">SECOND PAGE</a> |
  <a href="main2.php?third_page.php">THIRD PAGE</a>
  
<hr />  
  
<p>A demo of one way to assemble sites with PHP</p>

The rest is the same

Subdirectory containing the example files.

Exercise Lab 10

For this exercise, create a multi-page site.

It should use the template technique with a home page and a second page.

Design the template yourself. Include navigation for the home page and the second page

For the home page content, use the content from your Lab 09 page.

For the second page content, write a couple of paragraphs explaining how the templating technique works.

Be sure to add the lab to your table of contents page and to complete the entry on Blackboard.

Comments to: chang@hood.edu

Last Modified: 08 April 2008. 07:55