Is this code vunerable to \0 php
<p>I've read about null bytes \0 and read about file_exists not being secure... Can someone tell If this code is safe: Or how do I fix it?</p>

<pre><code>if (file_exists('controllers/' . $controller . '.php'))
</code></pre>

<p>This is the _action ("controller") variable, basically this is what $controller is validated with:</p>

<pre><code>$_action = ( (isset($_GET['r']) &amp;&amp; ctype_alnum($_GET['r'])) ? $_GET['r'] : $_default );
</code></pre>
