Make a form, and in the form tag put action="nameofphppage.php"
Also add method="post" or method="get". get puts the info in the browsers address bar, so it's good for things like searches. post hides the data, so it's good for lots of other things, like log in boxes.
Then to read the variables in php, they are stored in $_GET['X'] or $_POST['X'] where X is the name of the field in your form.