There are a couple ways you can do this. One is with an HTML meta tag (IF you want to redirect users from .html to your php page). To do this, add this into the <head> section of your HTML
<META HTTP-EQUIV=Refresh CONTENT="10; URL=http://www.yoursite.com/yourpage.php">
Where 10 is the time until they are forwarded, and the url is the page to forward to.
The other way is using PHP, you can send an HTML header using the following:
<?php
header("Location: http://www.yoursite.com/anotherpage.php");
?>
This command must be used before any data has been sent to the user. Also, it will forward them right away to "http://www.yoursite.com/anotherpage.php" without any delay.
Hope this helps,
-JoshB