Error: Invalid PathExpression. Must be a StateFieldPathExpression. - symfony

Question

I'm working on a symfony project entity with query builder. When I try to run this function I get this issue.
[Semantical Error] line 0, col 9 near 'category FROM': Error: Invalid PathExpression. Must be a StateFieldPathExpression.
public function json_filterAllproductsAction() {
$search = "";
$category = 1;
//Combine tables and create the query with querybuilder
$em = $this->container->get('doctrine.orm.entity_manager');
$qb = $em->createQueryBuilder();
$qb->select('p.category')
->from('EagleAdminBundle:Products', 'p')
->orderBy('p.id', 'DESC');
if ($category != 0) {
$qb->andWhere('p.category = :category')
->setParameter('category', $category);
}
$qb->andWhere('p.productTitle LIKE :title')
->setParameter('title', "$search%");
//convert to json using "JMSSerializerBundle"
$serializer = $this->container->get('serializer');
$jsonproducts = $serializer->serialize($qb->getQuery()->getResult(), 'json');
return new Response($jsonproducts);
}
I think error is in,
$qb->select('p.category')
It would be great help someone can help me.

Answer 1

You need to fetch category as well in your join. Something like this should work fine:
$qb->select('p', 'c')
->from('EagleAdminBundle:Products', 'p')
->orderBy('p.id', 'DESC')
->join('p.category', 'c');
if ($category != 0) {
$qb->andWhere('p.category = :category')
->setParameter('category', $category);
}
$qb->andWhere('p.productTitle LIKE :title')
->setParameter('title', "$search%");
Note if you don't want to limit your search to only products that have categories you can change the join to a leftJoin.
Also note you can have the serializer configured to serialize the category property of product. Then you should just be able to fetch a product and have it automatically serialize the category for you.