 <p>Try changing one of your href to <code>about.php</code> and see if it works. Example:</p> <pre><code> &lt;ul class="dropdown-menu" data-role="dropdown"&gt; &lt;li&gt;&lt;a href="about.php"&gt;About&lt;/a&gt;&lt;/li&gt; //etc </code></pre> <p>As it stands your hyperlinks go to your <code>index.php</code>, which gives that same value to the <code>PHP_SELF</code> super, thus never agreeing with <code>about.php</code>. At least that what I can see by this limited code sample. If that doesn't work, please edit your question to include the output of <code>$_SERVER['PHP_SELF']</code>, which should give you the clue anyway.</p> <p>Moreover there's no reason to use <code>strpos</code> when comparing strings; use the <a href="http://stackoverflow.com/a/80649/2194007"><code>===</code></a> operator instead, which checks if arguments are of the same <em>type</em> as well as if they have the same value.</p>