Displaying a div if a PHP if statement is true - php

Question

I have the following PHP script within a file named login.php
<?php
$ref = $_SERVER['HTTP_REFERER'];
if ($ref == 'http://example.com/dir/invalid.php' || $ref == 'http://www.example.com /dir/invalid.php') {
echo '
<div id="invalid">
TESTTESTTESTTESTTESTTESTTESTTEST
</div>
';
}
?>
I have deliberately went to the invalid.php page (which redirects using header() to login.php) and this div does not show up. Does it have something to do with the referrer not really being invalid.php or is there an issue with the script?
Thanks

Answer 1

I don't think the HTTP_REFERER is what you think it is. Namely, it is the page from which the user followed a link to the current page. However, it's very unreliable as we rely on the browser of the user to correctly report this value.
I would suggest the option I thought you needed, except that the only one I can think of you might doesn't really makes sense... (checking if the url matches a url that's not the current script)... so I do not see what you are trying to do.
As promised several ways to do what you want to achieve:
First off, I don't like this solution at all and really consider it ugly, but it's the one closest to what you where trying to do.
invalid.php
require 'login.php'; // we include the file instead of referring to it
login.php
if ($_SERVER['SCRIPT_NAME'] == 'invalid.php')
{
// do whatever
}
The main difference between what you did and what I did for the user will be that here the url bar will show that you're at invalid.php and not somewhere else. This also means that refreshing doesn't make the message go away.
A better solution in my opinion is the following:
In your script that logs a user in (checks the database and everything):
if (!valid_login()) // pseudo-code, obviously
{
$_SESSION['invalid_login'] = true;
header('Location: login.php');
// previously, we had something like this instead of the two lines above:
// header('Location: invalid.php');
}
in login.php
if (isset($_SESSION['invalid_login']) && $_SESSION['invalid_login'])
{
$_SESSION['invalid_login'] = false;
// do whatever
}
Of course, this should be done with proper session facilities like starting up the session in both those files. Instead of using session variables, you could include the file and use normal variables or send GET variables through the header request, but both those solutions share a problem: refreshing doesn't make the message disappear. However, if you were to move the code from the top file of the two above to login.php (if it's not already there, I don't know what file that actually is...) you could once again use normal variables instead of session variables and have a solution in which refreshing does make it go away. In this case, you might argue that you are cluttering your files with bussiness logic and presentation, but there are solutions to that (like keeping it in a separate file, and including it into login.php, moving the html to another file and including that one into login.php or both.