Obviously do I know the .htaccess solution to create subdomains. This is very handy if you don’t have cPanel or another web admin tool.

RewriteEngine On

RewriteCond %{HTTP_HOST} !^www\.yoursite\.com
RewriteCond %{HTTP_HOST} ([^.]+)\.yoursite\.com [NC]
RewriteRule ^(.*)$ http://www.yoursite.com/%1 [L,R]

This solution points to a folder in your root so it isn’t a very dynamic one. Lets see the solution!

Apache configuration

First you have to change the Apache configuration to make it by adding the following line to the httppd.conf file (the Apache configuration file).

ServerAlias *.yourdomain.com

Read more about this configuration on the Apache website.

Static subdomains

//array for static subdomains
$subdomains = array(
			'forum',
			'mobile',
			'demos',
			);

$match = preg_replace('#(http://)?(www\.)?(.+?)(\.yourdomain.com){1}#i','\\3', $_SERVER['HTTP_HOST']);

	if(in_array($match, $subdomains)){
		include('/root/yourdomain.com/'.$matc.'/index.php');
	}else{
		//Do normal stuff
	}

Dynamic sub domains

It is also possible to create the array from a database selection. See the following example:

//array for static subdomains
$subdomains = array(
			'forum',
			'mobile',
			'demos',
			);

$match = preg_replace('#(http://)?(www\.)?(.+?)(\.yourdomain.com){1}#i','\\3', $_SERVER['HTTP_HOST']);

	if(in_array($match, $subdomains)){
		include('/root/yourdomain.com/'.$matc.'/index.php');
	}else{
		$sql = "SELECT nickname FROM users WHERE nickname = ".$match;
		$res = mysql_query($sql);
		$rows = mysql_num_rows($res);

		if($rows == 1){
			//pointer to user profile page
			include('/root/yourdomain.com/profiles/index.php);
		}else{
			//Do normall stuff
		}
	}

NOTE!
This is a very basic way of creating subdomains. There are no build in checks or errorhandler. The way of naming your files and choosing a structure is whole yours.

Sessions

When you’re using sessions (a login system for example) the session will be lost you’re browsing to another (sub)domain. You can prevent this by adding the following line to your .htaccess file in the root of your site.

session.cookie_domain = "yourdomain.com"