Да, сорян, исправил, все работает...
Мда... Затупил. Всем спасибо!
function add_item()
{
$first_name = mysql_escape_string( $_POST['first_name'] );
$last_name = mysql_escape_string( $_POST['last_name'] );
$job_title = mysql_escape_string( $_POST['job_title'] );
$company = mysql_escape_string( $_POST['company'] );
$phone = mysql_escape_string( $_POST['phone'] );
$email = mysql_escape_string( $_POST['email'] );
$status = mysql_escape_string( $_POST['status'] );
$query = "INSERT INTO users (first_name, last_name, job_title, company, phone, email, status) VALUES ('".$first_name."', '".$last_name."', '".$job_title."', '".$company."', '".$phone."', '".$email."', '".$status."');";
mysql_query ( $query );
header( 'Location: '.$_SERVER['PHP_SELF'] );
die();
}