$db = new PDO("sqlsrv:Server=YouAddress;Database=YourDatabase", "Username", "Password");

new PDO("sqlsrv:server=[sqlservername];Database=[sqlserverdbname]",  "[username]", "[password]");

//use any of these or check exact MSSQL ODBC drivername in "ODBC Data Source Administrator"
$mssqldriver = '{SQL Server}';
$mssqldriver = '{SQL Server Native Client 11.0}';
$mssqldriver = '{ODBC Driver 11 for SQL Server}';

$hostname='127.0.0.1';
$dbname='test';
$username='user';
$password='pw';
$dbDB = new PDO("odbc:Driver=$mssqldriver;Server=$hostname;Database=$dbname", $username, $password);

$dsn = "sqlsrv:Server=server.dyndns.biz,1433;Database=DBNAME";
$conn = new PDO($dsn, "root", "P4sw0rd");
$conn->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );

$sql = "SELECT * FROM Table";

foreach ($conn->query($sql) as $row) {
    print_r($row);
}

try
{

    $conn = new PDO("sqlsrv:Server=$server_name;Database=$db_name;ConnectionPooling=0", "", "");
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

}
catch(PDOException $e)
{

    $e->getMessage();

}