Query Objects in PHP: Rich Filtering Without Leaking SQL Into the Domain

Book: Decoupled PHP — Clean and Hexagonal Architecture for Applications That Outlive the Framework Also by me: Thinking in Go (2-book series) — Complete Guide to Go Programming + Hexagonal Architecture in Go My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools Me: xgabriel.com | GitHub You ship a list endpoint. GET /orders . It returns the customer's orders, newest first. Clean. Then product wants a status filter. Then a date range. Then "only orders over 100 euros". Then pagination. Then sort by total, descending. Six months later the controller signature reads like a tax form, and the repository method that backs it is findByCustomerAndStatusAndMinTotalBetweenDatesOrderedBy(...) with nine parameters, three of them nullable. So you "fix" it. You let the caller pass a Doctrine QueryBuilder into the repository. Or worse: the use case starts assembling WHERE clauses as strings because that was the fastest way to add the next filter on a Friday. Now your application layer knows about table aliases and SQL operators. The domain speaks SQL, and the whole point of having a repository interface is gone. There is a shape that holds: a query object the domain builds, and an adapter that translates it into SQL. The caller describes what it wants in domain terms. The adapter decides how to fetch it. The leak, concretely Here is the version that grows out of control. Every new filter is another nullable parameter. public function search ( ?string $customerId , ?string $status , ?DateTimeImmutable $from , ?DateTimeImmutable $to , ?int $minTotalCents , string $sortBy = 'placedAt' , string $direction = 'DESC' , int $page = 1 , int $perPage = 20 , ): array ; Nine parameters, half of them nullable, two of them ( sortBy , direction ) carrying raw column names that map straight to SQL. Add a filter and the signature grows again. Every caller has to remember positional order. And $sortBy is a column name leaking through the port: t