<?php
// Doctrine_Manager controls all the connections 

$manager = Doctrine_Manager::getInstance();

// Doctrine_Connection
// a script may have multiple open connections
// (= multiple database connections)
$dbh     = new PDO("dsn","username","password");
$conn = $manager->openConnection();

// or if you want to use Doctrine Doctrine_DB and its 
// performance monitoring capabilities

$dsn     = "schema://username:password@dsn/dbname";
$dbh     = Doctrine_DB::getConnection($dsn);
$conn = $manager->openConnection();
?>