SQL for your
files, not just
databases.

use FQL\Query;

$query = <<<FQL
    SELECT *
    FROM (./feed.xml).SHOP.SHOPITEM
    WHERE
        EAN = "1234567891011"
        OR PRICE <= 200
    ORDER BY PRICE DESC
    LIMIT 10
FQL;

$results = Query\Provider::fql($query)
    ->execute()
    ->fetchAll();

use FQL\Query\Provider;
use FQL\Enum\Operator;

$results = Provider::fromFile('feed.xml')
  ->from('SHOP.SHOPITEM')
  ->select('PRODUCT', 'EAN', 'PRICE')
  ->where('PRICE',
    Operator::LESS_THAN_OR_EQUAL,
    500
  )
  ->orderBy('PRICE')->asc()
  ->limit(100)
  ->execute()
  ->fetchAll();