When I set the variable form a html select list it works properly.
When I dont set the variable it still executes, can you tell me why

PHP Code:
if(isset($_POST['sentto']) && ($_POST['sentto'] != '')) {
$jobsql "UPDATE job SET
    sentto = '
    WHERE jobid = '
$job' ";

mysql_query($jobsql)) {
"error adding to job table" mysql_error() . "sorry");
I just want to add that if I set the select option value in the form to have a not selected value of "0" and modify the != to be !='0' then it works and will not update that field