How do I add form fields to contact mailer?

hi,
i am very new to php…basically all i have done is made a simple contact mailer form like the ones in the tutorials section, with an email field,a message textarea, and a submit button. i want to make a form that has many more text fields, and a couple radio buttons. actually, i already have made that longer form, i just cant figure out how to write the php. so how does one add more fields to the php? here is the php for the little form that works:

<?php

$email = $_REQUEST[‘email’] ;
$message = $_POST[‘message’];

mail( "nandatown@gmail.com", “Contact Form Results”,
$message, “From: $email” );
header( “Location: http://www.nandatown.com/thankyou.html” );
?>

that sends me an email with a message…but how do i add more? lets say i want a field called “city” if i add:
$city = $_POST[‘city’];
to the php, it doesnt show up in the email.

any help is very helpful and appreciated

thanks!