How to use andWhere and orWhere in Doctrine?

WHERE a = 1 AND (b = 1 Or b = 2) AND (c = 1 OR c = 2)

How can i make this in Doctrine?

$q->where("a = 1");
$q->andWhere("b = 1")
$q->orWhere("b = 2")
$q->andWhere("c = 1")
$q->orWhere("d = 2")

this isnt correctly... Should be:

$q->where("a = 1");
$q->andWhere("b = 1")
   $q->orWhere("b = 2")
$q->andWhere("c = 1")
   $q->orWhere("d = 2")

but how can i make it? In Propel is function getNewCriterion, and in Doctrine...?

$q->where("a = 1")
  ->andWhere("b = 1 OR b = 2")
  ->andWhere("c = 2 OR c = 2")
  ;

Here's an example for those who have more complicated conditions and using Doctrine 2.* with QueryBuilder:

$qb->where('o.foo = 1')
   ->andWhere($qb->expr()->orX(
      $qb->expr()->eq('o.bar', 1),
      $qb->expr()->eq('o.bar', 2)
   ))
  ;

Those are expressions mentioned in Czechnology answer.

One thing missing here: if you have a varying number of elements that you want to put together to something like

WHERE [...] AND (field LIKE '%abc%' OR field LIKE '%def%')

and dont want to assemble a DQL-String yourself, you can use the orX mentioned above like this:

$patterns = ['abc', 'def'];
$orStatements = $qb->expr()->orX();
foreach ($patterns as $pattern) {
    $orStatements->add(
        $qb->expr()->like('field', $qb->expr()->literal('%' . $pattern . '%'))
    );
}
$qb->andWhere($orStatements);

Why not just

$q->where("a = 1");
$q->andWhere("b = 1 OR b = 2");
$q->andWhere("c = 1 OR d = 2");

EDIT: You can also use the Expr class (Doctrine2).