<?php
global $user;
if (!$user->uid) {
?>
<div id="register-button">
<p><a href="/user/register">Click Here to Register</a></p>
</div>
<?php
}
?>

I use this code to place in blocks or pages to show a link to the user registration page if the user is not currently logged in. An example is a block I have setup on the home page of http://www.lightentheload.net. If the user is logged in, the block goes away.

Drupal Check for User Login

drupal

PHP