$from = $_POST['from'];
$to = $_POST['to'];
$message = $_POST['message'];

$query  = "SELECT * FROM Users WHERE `user_name` = '$from' LIMIT 1";
$result = mysql_query($query);
while($row = mysql_fetch_array($result, MYSQL_ASSOC)) {
    $fromID = $row['user_id'];
} 

I'm trying to have $formID be the user_id for a user in my database. Each row in the Users table is like:

user_id | user_name | user_type
   1    |  Hristo   |   Agent

So I want $from = 1 but the above code isn't working. Any ideas why?