Unable to connect with SQLServer

Hi, i am using PHP 5.6.25 and YII2.0, i am trying to connect with SqlServer. i have installed the required extensions, but i am unable to connect with it. i can see that extension are being displayed in phpinfo. but when i try to create a model via GII, i am getting the error.

Here is my connection string.

return [

    'class' => 'yii\db\Connection',

    'dsn' => 'sqlsrv:server=localhost\SQLEXPRESS;database=dbname;MultipleActiveResultSets=false',

    'username' => 'username',

    'password' => 'pwd',

    'charset' => 'utf8',


i have also attached screenshots. PFA.

Please guide me where i am making mistake??

try to download sqlserver driver from microsoft site