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Symfony2 – Franz Jordán 2011
}
// ...
In this example, you first query for a Product object based on the product's id. This issues a
query for jus the product data and hydrates the $product object with that data. Later, when you
call$product->getCategory()->getName(), Doctrine silently makes a second query to find
the Categorythat's related to this Product. It prepares the $category object and returns it to
you.
What's important is the fact that you have easy access to the product's related category, but the
category data isn't actually retrieved until you ask for the category (i.e. it's "lazily loaded").
You can also query in the other direction:
public function showProductAction($id)
{
$category = $this->getDoctrine()
->getRepository('AcmeStoreBundle:Category')
->find($id);
$products = $category->getProducts();
}
// ...
In this case, the same things occurs: you first query out for a single Category object, and then
Doctrine makes a second query to retrieve the related Product objects, but only once/if you ask
for them (i.e. when you call ->getProducts()). The $products variable is an array of
all Product objects that relate to the given Category object via their category_id value.
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