PHP URL Variables

In brief: I have a main.php file which ‘includes’ the middle section depending on the menu choice. The menu works by being <A href="?page=news">News</A> for example. So the main.php is called again with a page variable being passed. In the main.php I have this code:

if($page=='home'){
	include ('home.php');
}elseif($page=='news'){
	include ('news.php');
}else{
	include ('home.php');
}

My problem is that I have this hosted in two places. On my own hosting it seems to work perfectly fine. However on hosting that has been bought by the company for it, it doesnt. And home.php is displayed all the time. As far as i understand it php is available on the new hosting, as I can view pages, for example, that are created by php using mySql info. Its just these links that do not seem to work!! any ideas??