I've purchased a book "Beginning PHP4", and I've got a problem. In chapter 8, when it comes to switch pages using a $PHP_SELF global variable, I encounter a problem about undefined variable called $action. Here's the source code:

<?php
//selector.php
switch ($action)
{
   case "order_food":
      include "./waiter.php";
   break;
   case "play_hangman":
      include "./hangman.php";
   break;
   default:
      echo "Please choose what you'd like to do:<BR>";
      echo "<A HREF=$PHP_SELF?action=order_food>Order Food</A><BR>";
      echo "<A HREF=$PHP_SELF?action=play_hangman>Play Hangman</A>";
}
?>

When I run this on my local server, I get a following error:
"Notice: Undefined variable: action in c:\Inetpub\wwwroot\selector.php on line 3"

Is there any way to define the $action variable so I can switch pages?

$action has not yet been defined. Just because the default case is present, that doesnt mean that the switch can validate an uninitialized variable. At the beginning of your script I would add:

$action = "";
if (isset($_GET['action']))
     $action = $_GET['action']

That should fix that error. You may also want to turn register_globals on in your php.ini, although thats not a good thing to get in the habit of doing.

Jeff

Function register_globals is already turned on in my php.ini file. When I've added the code you posted, everything worked fine, but when I clicked on any choice, I get the following error code:

Parse error: syntax error, unexpected T_SWITCH in c:\Inetpub\wwwroot\selector.php on line 6

How can I avoid this?

Sorry, I typed the code freehand without checking it. Add a semi-colon (;) after the
$action = $_GET['action'] line. Im surprised php ran initially without that.

I would remove the first line
$action = "" ; <---- will reset the value of action everytime page loads and we don't want that.


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Never bother to learn something not knowing which does not do you any harm, and never neglect to learn something whose negligence will increase your ignorance - Imam Jafar Sadeq

Yeah, but that would return an error about undefined variable again, and that really is what we don't want. It's much easier to add $PHP_SELF global variable to every hyperlink in the script than to bother with this.

you can always add this line to the top of your pages:

error_reporting(0);


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Never bother to learn something not knowing which does not do you any harm, and never neglect to learn something whose negligence will increase your ignorance - Imam Jafar Sadeq