Testing a Database for TRUE/FALSE using AJAX/PHP/SQL - php

Question

Let me begin with stating that you are about to see that I am still using some Mysql code in this question. It is only because I am new to PDO and in an effort to troubleshoot, I wanted to make sure my sql and queries were working so I went with what I know. Once I get the function working and the scripts running, I will convert to PDO.
Heres the question I have. I am submitting a form that subscribes a user to a email list (database). It takes all their info and inserts it into a DB. So far this all works. My Call back function is then supposed to check to see if this user was already in the DB or not.
I was testing to see if a row got returned from the DB based off of the email column being set as a unique column. The problem is that even though the user is already in the DB, the sql returns a line saying "Duplicate entry", so my code is reading the line DUPLICATE ENTRY as a result. Can someone point me in the right direction?
My jQuery code...
$('#contForm').submit(function() { //contForm is the name of my form
var formData = $(this).serialize();
$.post('contact.php',formData,dispAdd); //dispAdd is the callback
function dispAdd(result) {
if (!result) {
$('#main').html('<div>Your have been added to the mailing list</div>');
} else {
if ($('#fail').length==0) {
$('#main').append('<div id="fail">This email address is already subscribed to our mailing list</div>');
}
}
}
return false;
});
My PHP/SQL script
function dispAdd()
{
$email= $_POST['email'];
$sql= "SELECT * FROM mailList WHERE email = '$email'";
$result= mysql_query($sql) or die(mysql_error());
$rows = array();
if(mysql_num_rows($result) > 0)
{
while ( $row = mysql_fetch_assoc($result)) {
$rows[] = $row;
}
echo json_encode( $rows );
}

Answer 1

After playing around a lil more I figd out how to make it work but if anyone has other tips or ideas Im happy to hear them. I learn a lot on here so Im welcome to all comments please. Here is how I made it work:
function dispAdd()
{
$email= $_POST['email'];
$sql= "SELECT * FROM mailList WHERE email = '$email'";
$result= mysql_query($sql) or die(mysql_error());
if(mysql_num_rows($result) > 0)
{
while ( $row = mysql_fetch_assoc($result)) {
}
return;
}
}