PHP form help

Right now i’ve got a form that has name, subject, and message text boxes. the forms works, but I want to add more input boxes. I added another box and named the variable name as business, but I don’t know how to make my php code properly post this extra variable so that when I recieve the email it shows up. Can anyone help me?

<?

$to = “[email protected]”;
$msg = "$name

";
$msg .= "$message

";
$msg …= "$business

";
mail($to, $subject, $msg, "From: my website
Reply-To: $email
");
?>