You'll have to use an input field no matter what. You'll just make the input field invisible to the user.
<input type="hidden" name="input" value="info you want to submit">
Then you'll use $_GET $_POST or whatever to get the info.
This question is borderline PHP. So you might want to ask to have it moved if you plan to discuss PHP related aspects.
Of course if the info you are wanting to submit is always going to be the same, a timestamp, or some kind of php function, etc you could set up a variable in your PHP page.
$myinfo = "blah";