$result_id = $db->query('SELECT id FROM groups ORDER BY id DESC LIMIT 1');
foreach($result_id as $row_id) {
print $row_id['id'];
$id = ( int )$row_id + 1;}
print $id;
$db->exec("INSERT INTO groups(id, string_a,string_b) VALUES ($id, $string_a, $string_b);");