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I'm helping a client with an older website an am coming across code which was written several years ago (not sure if this is relevant, but I mention it just in case) and keep getting an Undefined index error, despite using the various suggestions (namely isset) mentioned on the site. Mostly I'm moving files over from the older server, where the site worked fine, so I'm not sure why I'm getting this error. I'd assume is has something to do with the variable 'sessionID' not being set, but I cannot find anywhere in the existing code where it is set - 

<?php
session_start();
error_reporting(E_ALL);
if ($_SESSION['sessionID'] != session_id() || !$_SESSION['userID']) { 
// login page   
} else {
// admin page
}
?>
Scott Again
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    If you are not sure if it is set. Please `var_dump` it so you know the exact value. What does it return? – Jelmer Dec 16 '12 at 21:13
  • How have you attempted to use `isset()`? It would mitigate as `if (!isset($_SESSION['sessionID']) || $_SESSION['sessionID'] != session_id())` Note this does not address _why_ you would store `session_id()` into `$_SESSION` in the first place) – Michael Berkowski Dec 16 '12 at 21:17
  • var_dump returns array(0) { } – Scott Again Dec 16 '12 at 22:24
  • MB your suggestion worked well - I'm not sure how to accept that as the answer and close the inquiry, there's no checkmark next to it.. – Scott Again Dec 17 '12 at 18:48

2 Answers2

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A PHP error consists of all the information needed to debug a problem. It provides:

  1. The error level (E_WARNING, E_NOTICE, E_ERROR, etc...).
  2. A short message that usually describes the problem (in your case Undefined index along with the name of the variable in which the undefined index is used).
  3. The name of the PHP script where the error occurs (this includes the full path to the script on your system so that you can locate it easily).
  4. The line number on which the error handler was invoked (this is precisely where the error occurred in that file).

Here's an example of a PHP error like the one you got...

Notice: Undefined index: sessionID in /tmp/test.php on line 2

You have everything you need to figure out how you got this error right there. What I can tell you by looking at this error message, for example, is that as of line 2 in the file /tmp/test.php I had not defined the index sessionID in the array $_SESSION.

This is easily solved by always checking that the variable is defined first with isset().

if (isset($_SESSION['sessionID']) && $_SESSION['sessionID'] != session_id()) {
    // login page 
} else {
    // admin page
}
Sherif
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  • That the variable was not defined in that file is pretty apparent, what I can't figure out is why it worked in the previous live site, and not now, since all the files are the same. I've tried isset in the existing configuration, it didn't work, and I tried the code you posted, it passed me straight through to the admin page without having to login. Basically I'm trying to make a secure login page, but trying to use the same code as was handed to me (client's request) - I'm not sure why the original coder made the decisions they made. – Scott Again Dec 16 '12 at 22:02
  • _doesn't work_ doesn't tell me anything useful. The variable not being defined up until the line of code mentioned in the error is enough to start tracing your steps back to figure out what went wrong that it didn't get set. What other errors did you get? If by **it worked in the previous live site** you mean you didn't see those errors that's a completely different issue. You haven't provided any useful information to help you further debug the problem. No error messages and that code out of context gives me nothing more to go on. `var_dump` your variables. Show more code in context. – Sherif Dec 16 '12 at 22:37
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Undefined index is a Notice, not an Error. Set error_reporting(E_ALL ^ E_DEPRECATED ^ E_NOTICE) and see if that fixes everything.

Ray Paseur
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    Notices should be dealt with too. Otherwise, you're just sweeping poor coding practices under the rug. Sooner or later, an important E_NOTICE will be missed. – Michael Berkowski Dec 16 '12 at 21:18
  • Couldn't agree more, but the likely "correct" solution is refactoring and that raises cost and schedule implications. Big cost and schedule implications since the old code probably relies on a lot of early PHP assumptions. – Ray Paseur Dec 16 '12 at 21:21