PHP if statements unsure where I'm wrong

Question

I'm trying to specify that my logo appears on some pages and not on others, the only pages I do not want it showing on are the homepage and /index.php. I have the big logo appearing and disappearing as I want it and so I presumed I could just do the opposite for the small logo but I must be doing something wrong. Here is my current code:

<?php
$dunpage = $_SERVER['REQUEST_URI']; if ($dunpage != '/index.php' || $dunpage != '/') {?>      
<h1 class="small-logo">
<a href="/" title="<?php echo $siteName; ?>"><span><?php echo $siteName; ?></a>
</h1>
<?php } 
?>
<?php
$currentpage = $_SERVER['REQUEST_URI']; if ($currentpage == '/' || $currentpage == '/index.php') {?>
<h1 class="logo";>
  <a href="/" title="<?php echo $siteName; ?>"><span><?php echo $siteName; ?></a>
</h1>
<?php } 
?>

Answer 1

Instead of a logical OR in your first condition, you should be using a logical AND:

$dunpage = $_SERVER['REQUEST_URI']; if ($dunpage != '/index.php' || $dunpage != '/') {?> 
// Should be
$dunpage = $_SERVER['REQUEST_URI']; if ($dunpage != '/index.php' && $dunpage != '/') {?> 

Effectively, you were saying "act if the page is either not index.php, or not /." So in either of those cases, the opposite would be true. If it wasn't index.php, it could be /, for example.