try {
 $query = $dbh->query("SELECT name, city FROM schools WHERE 1 GROUP BY name,
 city");
 $query->setFetchMode(PDO::FETCH_ASSOC);   //THIS IS LINE 21 error refers to
 $iterator = new IteratorIterator($query);
 foreach ($iterator as $row) {
 if (empty($row['name']) == false && !in_array($row['name'], $name_list))
        $name_list[] = $row['name'];
    if (empty($row['city']) == false && !in_array($row['city'], $city_list))
        $city_list[] = $row['city'];
 }