How can I make sure someone uses www.domain.com instead of domain.com

[IH-James]

It is very easy to make sure that a user uses http://www.domain.com instead of just http://domain.com with a simple piece of PHP code placed at the top of every page.

PHP Code:

<?php
$server = getenv("HTTP_HOST");

if (!ereg("^www.", $server)) {
    // Assume no www. has been entered
    Header ("Location: http://www.".$server."/");
    Exit;
     
}
?>

Alternatively, you can also use mod_rewrite in your .htaccess file. Put it inside your public_html directory in order for the changes to effect all files/directories.

RewriteEngine On
Options +FollowSymlinks
RewriteCond %{HTTP_HOST} ^domain\.com
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=permanent,L]

Replace domain and .com as necessary.