Logout link for Joomla 1.5, 2.5 and 3.0

Logout.php

Joomla 1.5 Logout Link
<?php
$returnURL = base64_encode(JURI::root() . "");
$user =& JFactory::getUser();
echo 'Hi,'.$user->username;
?>
<a href="index.php?option=com_user&task=logout&return=<?php echo $returnURL; ?>">Logout</a>

Joomla 2.5 Logout Link
<a href="index.php?option=com_users&task=user.logout&<?php echo JUtility::getToken(); ?>=1">Logout</a>

Joomla 3.0 Logout Link
<a href="index.php?option=com_users&task=user.logout&<?php echo JSession::getFormToken(); ?>=1">Logout</a>


Source: http://rselvakumar.blogspot.fr/2013/02/logout-link-for-joomla-15-and-25.html