PHP Yii framework ทำไงให้สามารถ เลือก select dynamic Database ได้หลายตัวอะครับ

'db' => require(__DIR__ . '/db.php'),
'db2' => require(__DIR__ . '/db2.php'),

Yii::$app->db;
Yii::$app->db2;

  'db' => array(
            'connectionString' => 'sqlsrv:Server=127.0.0.1;Database=test;',
            'username' => 'sa',
            'password' => 'test',
            'charset' => 'utf8',
        ),
        'db2' => array(
            'connectionString' => 'sqlsrv:Server=127.0.0.1;Database=test2;',
            'username' => 'sa',
            'password' => 'test',
            'charset' => 'utf8',
            'class' => 'CDbConnection'
        ),

$query = $connection->createCommand("SELECT * FROM xxxx");
$result = $query->queryAll();
// หรือ?
$result = $model->find();

$query = Yii::app()->db->createCommand(select * from xxx);
หรือ 
$query = Yii::app()->db2->createCommand(select * from xxx);


$result = $query->queryAll();

<select id="database">
<option value="1">Database 1</option>
<option value="2">Database 2</option>
</select>

$query = Yii::app()->db->createCommand(select name from master..sysdatabases where name like 'test%');
$re = $query -> queryAll();
$str = "<select id="database">";
$i=1;
foreach($re as $reall){
$str += "<option value=$i>$reall['name']</option>"
$i++;
}
$str += "</select>";
echo $str;

class Mainbase
{
	public $db = [
		'host'	=> 'localhost',
		'user'	=> 'ckung',
		'pass'	=> '123!@#',
		// 'base'	=> 'pd_001',
	];
	public $connect;

	public function __construct()
	{
		$host	= $this->db['host'];
		$user	= $this->db['user'];
		$pass	= $this->db['pass'];
		// $db		= $this->db['base'];
		try {
			// $this->connect = new PDO("mysql:host={$host};dbname={$db}", $user, $pass);
			$this->connect = new PDO("mysql:host={$host};", $user, $pass);
		}
		catch (Exception $e) {
			$this->connect = die("Unable to connect: " . $e->getMessage());
		}
	}

	public function query($sql)
	{
		$output = [];
		if(is_array($sql)){
			try {
				$dbh = $this->connect;
				$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
				$dbh->beginTransaction();
				foreach($sql as $sql){
					$dbh->exec($sql);
				}
				$dbh->commit();
				$output[0] = true;
			}
			catch (Exception $e){
				$dbh->rollback();
				$output[0] = false;
				$output[1] = $e->getMessage();
			}
		}
		return $output;
	}

	public function select($sql)
	{
		$output = [];
		if(is_array($sql)){
			try {
				$dbh = $this->connect;
				$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
				$output[1] = [];
				foreach($sql as $sql){
					$command = $dbh->query($sql);
					$result = $command->fetchAll();
					$output[1][] = $result;
				}
				$output[0] = true;
			}
			catch (Exception $e){
				$output[0] = false;
				$output[1] = $e->getMessage();
			}
		}
		return $output;
	}
}
$baseapp = new Mainbase;

$baseapp->query(["use pd_006;"]);
$data = $baseapp->select([
	"SELECT * FROM province",
	]);
print_r($data[1]);