Simon’s solution is certainly suitable, however it seems needlessly complex. Might I suggest doing the following:
$page = $_GET["page"];
PHP does interpret variables inside of strings delimited by double quotes, and I use this approach on all of my work without a hitch.
If you are concerned about people deliberately trying to enter invalid values for the page variable, you could simply define an array of valid pages and check it. You might also want a default page value in case someone just goes to your TLD:
$defaultPage = "home";
$validPages = array("home", "news", "community", "resources", "store", "tos", "error");
$page = (isset($_GET["page"])? $_GET["page"] : $defaultPage);
$page = "errorPage";
Then all you have to do is create errorPage.php to show some sort of error indicating that the user has entered an unrecognized value for the $page variable. Again we’ve eliminated the if statements (which are somewhat slow, and in this case unnecessary).
In the end it’s your decision how to implement it, and both of these approaches are satisfactory, but I just wanted to provide another alternative (probably since I’m partial to my own solution!). Hope that helps a bit.