On SESSION_DESTROY decrease the number of online users in PHP
<p>I have a simple file-system-ed-login (not mysql) just to track number of users who are registered to my website.</p>

<p>I want to know who are all online too.</p>

<ol>
<li>When the browser is closed the session is destroyed automatically.</li>
<li>I use a explicit logout command too.</li>
<li>I can handle the number of online users on pressing "logout" button, thus by reducing the count in file "nouser.txt" which handles the number of users who are online.</li>
</ol>

<p>So the thing I want to know is, if the user closes his browser with out pressing "logout", though the session_destroy() clears out the login implicitly, I want to decrease the number of online users in the nouser.txt file</p>

<p>edit 1:
Just like handling onSession_Destroy() on closing the browser.</p>
