form post question

I have a form which has the following: ( quick clip ) <form id="form1" name="form1" method="post" action="http://www.abc.com/processing/process_form.php" onSubmit="return preSubmit();"> <label> <input name="area_interest" type="checkbox" id="field13" value="Peer Guide" /> Peer Guide</label> <br /> <label> <input type="submit" value="Submit" /> When the form runs process_form.php it emails the content and has several other fields from the form, but I have some fields like the one above that don't show up in the result. The script that builds the message looks like the below $temp_message .= "Area(s) of Interest: ". $_POST['area_interest'] ."\n"; Is there anything obvious that I am missing? Is there a way for me to show all the fields from the form, and their field names which are received by process_form? Thanks! Jack