Creating a Hit Counter | Spring Into PHP 5

Here's an example that points out the advantages of using sessions. Say you want to create a hit counter that keeps track of the number of times a user has visited a specific page. If you try to simply increment a variable, $counter, as shown in phpcounter.php, Example 9-14, there will be a problem because the data in that variable is not preserved between page accesses.

Example 9-14. Hit counter first try, phpcounter.php

 <HTML>     <HEAD>         <TITLE>             A hit counter         </TITLE>     </HEAD>     <BODY>         <CENTER>             <H1>                 A hit counter             </H1>             Welcome. You've been here             <?php                 $count++;                 echo $count ;             ?>             times before.         </CENTER>     <BODY> </HTML>

As shown in Figure 9-13, no matter how many times you load the page, the counter will always be reset (and you'll get a notice about incrementing an undefined variable).

Figure 9-13. First attempt at a hit counter.

The solution is to store the count in a session, as you see in Example 9-15.

Example 9-15. Corrected hit counter, phpcounter.php

 <HTML>     <HEAD>         <TITLE>             A hit counter         </TITLE>     </HEAD>     <BODY>         <CENTER>             <H1>                 A hit counter             </H1>             Welcome. You've been here             <?php                session_start();                if (!isset($_SESSION['count'])) {                    $_SESSION['count'] = 0;                } else {                    $_SESSION['count']++;                }                echo $_SESSION['count'];                ?>             times before.         </CENTER>     <BODY> </HTML>

You can see the final working version in Figure 9-14. Nice.

Figure 9-14. The working hit counter.