php e-mail form. how to attach 4th parameter?

i have a problem with mail form.i know that i can send 3 parameters from my form but i heard that i can just add 4th parameters. for example in the MESSAGE i can attach TELEPHONE.the problem is that i dont know how to do that, because i am new in php. anyone can help? this is a code:

<?php
if ($_REQUEST['name'] && $_REQUEST['email']&& $_REQUEST['message'])
{
mail ('[email protected]','Contact Form: from '.$_REQUEST['name'], $_REQUEST['email'], $_REQUEST['message']);

} ;
?>

There are tons of examples on php.net for how to use the mail function.