$conn=new PDO("mysql:host=$servername;dbname=meuDB", $username, $password);

$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$conn=PDO_connect("host=$servername;dbname=meuDB", $username, $password);

$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$conn= new PDO("odbc://$servername:3306/dbname", $username, $password);

$conn->setAttribute(dbname, "meuDB");

$conn=PDO_connect("host://$servername:3306;dbname=?", $username, $password);

$conn->setParameter(dbname, "meuDB");

$conn=new PDO("mysql_host=$servername;dbname=?", $username, $password);

$conn->setParameter(1, "meuDB");