findOneBy

findOneBy is a method commonly used in Doctrine ORM repositories to fetch a single entity that matches a set of field-value criteria. It is part of the repository interface and provides a convenient way to perform simple lookups without writing a full query. The method signature is findOneBy(array $criteria, array $orderBy = null).

Criteria is an associative array where keys are entity field names and values are the values to match. Doctrine translates this into a query that returns at most one result. The query is limited to one result (LIMIT 1). If multiple entities satisfy the criteria and an orderBy is supplied, the first result according to that order is returned. If no orderBy is provided, the result is not guaranteed to be deterministic across databases or executions.

The method returns the matching entity or null if none exists. This makes findOneBy convenient for unique lookups or quick existence checks where only a single entity is needed.

Examples:

- $user = $entityManager->getRepository(User::class)->findOneBy(['email' => '[email protected]']);

- $latestPost = $entityManager->getRepository(Post::class)->findOneBy(['author' => $author, 'status' => 'published'], ['publishedAt' => 'DESC']);

Relation to other repository methods: findOneBy differs from findBy in that it returns a single entity (or null) instead of an array of entities. For retrieving by primary key, use find($id). For more complex queries, consider using QueryBuilder or DQL.