variable is not set (chapter 13)

mcandw · August 20th, 2004, 05:29 PM

Hello all,
I'm really having torubles trying to figure this one out, I'm wondering if there is an error in the code supplied in the book, or if I am missing something obvious.
My questions refers to the register.php file from Chapter 13.

SOmeone else already asked my first question:

Quote:

quote:
the file either displays a form or registers the users submitted details. the Switch below determines whether the form has been submitted or not:

switch($action) {
   case "register":
      create_account();
   break;
   default:
      html_header();
      register_form();
      html_footer();
   break;
}

i am recieving the following error when i load the file:
Notice: Undefined variable: action in ...

which makes sense to me as the hidden field in the form "action" has not yet been submited.

so why does this code expect the variable "action" to be defined before it is???

Response:
--------------------------------------------------------------------------------

That means $action didn't exist before you tried using it, add a check of the variable's existence before the switch.

if (isset($action))
{
   switch($action) {
      case "register":
         create_account();
      break;
      default:
         html_header();
         register_form();
         html_footer();
   }
}

Now, that all makes sense, but what I dont understand is that if the $action variable isn't set, how can the code in the book get this to work without an If statement?
And the other problem is that the first time the page is opened, $action will not be set, so even register_form() won't execute, meaning that we won't even see the form in the first place!

Am I missing something obvious? SOmeone please enlighten me...
Thanks a lot,
Alex

mcandw · August 20th, 2004, 05:38 PM

Well, I just read the Chapter 12 discussion about the same topic (sorry that I didn't read it earlier), and I used the following:

    switch($_POST["action"])
    {
        case "register":
           DoSignup();
        break;
        default:
                   //do other stuff
        break;
      }

Whcih works, but I'm not sure exactly waht it's doing. If anyone cares to explain, I wold be forever indebted... ;)

richard.york · August 20th, 2004, 05:52 PM

First, have a read of my reply at this thread:
http://p2p.wrox.com/topic.asp?TOPIC_ID=17719

Quote:

quote:
Now, that all makes sense, but what I dont understand is that if the $action variable isn't set, how can the code in the book get this to work without an If statement?
And the other problem is that the first time the page is opened, $action will not be set, so even register_form() won't execute, meaning that we won't even see the form in the first place!

Beginning PHP 4 is a pretty old book, it was written using a very early version of PHP 4. At that time, PHP was much more loose, so the code in the book reflects that. PHP has since evolved and become more explicit.

Code:

switch($action) {
   case "register":
      create_account();
   break;
   default:
      html_header();
      register_form();
      html_footer();
   break;
}

This code takes into account that $action doesn't exist or contain a value by the default case of the switch loop, which means wrapping in if (isset($action)) isn't an appropriate fix here. An appropripriate fix that offers the same functionality is:

Code:

if (!isset($action))
{
    $action = '';
}

switch($action) {
   case "register":
      create_account();
   break;
   default:
      html_header();
      register_form();
      html_footer();
   break;
}

This gives $action a value by initializing it and let's the original code retain its logic. So what's good about this? This goes back to my talk about validation and knowing what values to expect in your variables, which I mentioned in the thread above. By developing with NOTICE level errors you naturally write more explicit and more secure code.

The truth is Beginning PHP4 is outdated! Most of the examples in that book just don't jive with current best practice.

register_globals is another common question, find answers here:
http://p2p.wrox.com/archive/beginnin...2002-11/17.asp

HTH!

Regards,
Rich

--
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mcandw · August 20th, 2004, 06:13 PM

Thanks for your quick reply!

I'm glad that there was in fact something wrong with the code, and that it wasn't just me not understanding.

As per your suggestion I may buy the new book, as I have found several issues throughout the book that I am displeased with, although I'm still very glad I own it.

Thanks a lot for your help once again.
Alex