Question

I can’t figure out why this script isn’t working.

<?php

if (($_GET['p'] != 'index') && 
    ($_GET['p'] != 'reg') && 
    ($_GET['p'] != 'login') && 
    ($_GET['p'] != 'ad') && 
    (!isset($_GET['p']))):
?>

<?php endif; ?>

I want to not display the error page if the $_GET is not set, which in my experience (!isset($_GET['p'])) should do.

Answer 1

If $_GET['p'] is not set, you can’t check $_GET['p'] != 'index' and all the others. You’ll have to check if it’s set first:

<?php if(
    ! isset( $_GET['p'] ) ||
    ($_GET['p'] != 'index' &&
    $_GET['p'] != 'reg' &&
    $_GET['p'] != 'login' &&
    $_GET['p'] != 'ad')
): ?>

---

A better solution would be to put all those values in an array, and check if $_GET['p'] is in the array:

<?php if(
    ! isset( $_GET['p'] ) ||
    ! in_array(
        $_GET['p'],
        array('index', 'reg', 'login', 'ad')
    )
): ?>

---

EDIT:

Now that you provided some more info, here’s what you should do:

if ( ! isset($_GET['p']) )
{
    // We're at the index page, so don't display anything
}
else
{
    if ( in_array( $_GET['p'], array('index', 'reg', 'login', 'ad') ) )
    {
        // Display your content window
    }
    else
    {
        // $_GET['p'] is not a valid value, display error
    }
}