LARAVEL Case Studies & Practical Application 4

Question 1

A Laravel app has a users table and a roles table with a many-to-many relationship. A query for all admins is returning duplicate users. What is the Eloquent fix?

Accepted Answer

Add ->distinct() or use whereHas('roles', fn($q) => $q->where('name', 'admin')) instead of a JOIN

Answer

whereHas() issues an EXISTS subquery that avoids duplicate rows without needing DISTINCT or GROUP BY.

Question 2

You are building a RESTful API and want to transform Eloquent models into consistent JSON responses (hiding certain fields, renaming keys, adding computed fields). Which Laravel feature is purpose-built for this?

Accepted Answer

API Resources (JsonResource and ResourceCollection)

Answer

API Resources provide a transformation layer between models and JSON responses, supporting field hiding, renaming, and computed properties.

Question 3

A subscription app must prevent a user from subscribing twice to the same plan. The check and insert happen in two separate database calls. Under concurrent requests, a race condition causes duplicate subscriptions. What is the correct fix?

Accepted Answer

Wrap the check and insert in a DB::transaction() with a SELECT ... FOR UPDATE lock or use firstOrCreate() with a unique index

Answer

A unique database index is the ultimate guard, and SELECT FOR UPDATE inside a transaction prevents concurrent reads from both passing the check.

Question 4

Your application must support multiple payment gateways (Stripe, PayPal, Square) and allow switching between them via a config value. What design pattern should the Laravel service container enforce?

Accepted Answer

Bind a PaymentGatewayInterface in the container and resolve the concrete class based on config('payment.driver')

Answer

Binding an interface in the service container and resolving based on config enables runtime gateway switching without changing calling code.

Question 5

A content management Laravel app uses soft deletes. An editor accidentally deleted an article. Which Eloquent method restores it?

Accepted Answer

Article::withTrashed()->find($id)->restore()

Answer

withTrashed() includes soft-deleted records in the query scope, and restore() sets deleted_at back to null.

LARAVEL - Laravel PHP Framework Practice Test

LARAVEL - Laravel PHP Framework Practice Test

LARAVEL Case Studies & Practical Application 4