protected static function connectModel($model, $host)
{
// cached handle is not null
// and new host is null
// use cached
if (self::$db_handle !== null && $host === null) {
$model->setDBH(self::$db_handle);
} elseif ($host !== null) {
// use a new host
$dbh = DBPool::getConnection($host);
$model->setDBH($dbh);
} elseif (self::$db_handle == null && $host == null) {
// db_handle is null and host is null
// (initiate default)
$handle = DBPool::getDefCX();
$model->setDBH($handle);
self::$db_handle = $handle;
}
}