API routes in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Laravel API route response?

Consider this Laravel API route code. What JSON response will the client receive when accessing /api/user?

Laravel

<?php

use Illuminate\Http\Request;
use Illuminate\Support\Facades\Route;

Route::get('/user', function (Request $request) {
    return response()->json(['name' => 'Alice', 'role' => 'admin']);
});

A {"name":"Alice"}

B {"user":{"name":"Alice","role":"admin"}}

C SyntaxError: Unexpected token in JSON

D {"name":"Alice","role":"admin"}

💡 Hint

Look at the array passed to response()->json() and how it converts to JSON.

The route returns a JSON response with keys 'name' and 'role' directly, so the output is a JSON object with those keys and values.

📝 Syntax

intermediate

Which option correctly defines a POST API route in Laravel?

You want to create a POST API route at /api/login that calls LoginController@login. Which option is correct?

A Route::post('/login', 'LoginController@login');

B Route::get('/login', [LoginController::class, 'login']);

C Route::post('/login', [LoginController::class, 'login']);

D Route::post('/login', function() { return LoginController@login(); });

💡 Hint

Use the array syntax with the controller class and method for API routes.

Option C uses the correct HTTP verb 'post' and the recommended array syntax with the controller class and method name.

🔧 Debug

advanced

Why does this Laravel API route return a 404 error?

Given this route definition, why does accessing /api/profile return a 404 error?

Route::get('/user/profile', function() {
    return ['profile' => 'data'];
});

A The route URL is '/user/profile', so '/api/profile' does not match and returns 404.

B The route is missing a controller, so it cannot be found.

C The route method should be post, not get, for '/api/profile'.

D The route callback returns an array instead of a JSON response, causing 404.

💡 Hint

Check the exact URL path defined in the route and the URL you are accessing.

The route is defined for '/user/profile', but the request is to '/api/profile'. They do not match, so Laravel returns 404.

❓ state_output

advanced

What is the output of this Laravel API route with middleware?

This route uses the 'auth:sanctum' middleware. What happens when an unauthenticated user accesses /api/dashboard?

Route::middleware('auth:sanctum')->get('/dashboard', function () {
    return ['message' => 'Welcome to your dashboard'];
});

A HTTP 404 Not Found error

B HTTP 401 Unauthorized error response

C {"message":"Welcome to your dashboard"}

D HTTP 500 Internal Server Error

💡 Hint

Middleware 'auth:sanctum' requires authentication before allowing access.

If the user is not authenticated, the 'auth:sanctum' middleware blocks access and returns a 401 Unauthorized response.

🧠 Conceptual

expert

How does Laravel API route caching affect route changes?

You run php artisan route:cache in your Laravel project. What is the effect on API routes if you later add a new route in routes/api.php without clearing the cache?

A The new route will NOT be recognized until you clear and rebuild the route cache.

B The new route is automatically detected and works immediately.

C The application throws a syntax error on any new route added after caching.

D The new route is added but only accessible via web routes, not API.

💡 Hint

Route caching stores routes in a compiled file for speed but requires manual refresh after changes.

Route caching compiles all routes into a cache file. New routes added after caching are ignored until cache is cleared and rebuilt.

Practice

1. What is the main purpose of defining API routes in Laravel's routes/api.php file?

easy

A. To configure middleware for user authentication

B. To define web page routes that return HTML views

C. To store database connection settings

D. To handle requests from other apps or devices and return JSON responses

Solution

1. Step 1: Understand the role of API routes

   API routes are designed to handle requests from external apps or devices, not for web pages.

2. Step 2: Identify the correct file and response type

   In Laravel, API routes are placed in routes/api.php and usually return JSON data.

3. Final Answer:

   To handle requests from other apps or devices and return JSON responses -> Option D

4. Quick Check:

   API routes = handle external requests + JSON [OK]

Hint: API routes handle external requests and return JSON [OK]

Common Mistakes:

• Confusing API routes with web routes that return HTML
• Thinking API routes are for database settings
• Assuming API routes are only for middleware

2. Which of the following is the correct syntax to define a GET API route in Laravel that returns a JSON message "Hello World"?

easy

A. Route::get('/hello', function () { return response()->json(['message' => 'Hello World']); });

B. Route::post('/hello', function () { return 'Hello World'; });

C. Route::get('/hello', function () { return view('hello'); });

D. Route::put('/hello', function () { return response('Hello World'); });

Solution

1. Step 1: Identify the HTTP verb and response type

   The question asks for a GET route that returns JSON data.

2. Step 2: Check each option's method and return

   Route::get('/hello', function () { return response()->json(['message' => 'Hello World']); }); uses GET and returns JSON with response()->json(), which is correct. Others use wrong verbs or return types.

3. Final Answer:

   Route::get('/hello', function () { return response()->json(['message' => 'Hello World']); }); -> Option A

4. Quick Check:

   GET + JSON response = Route::get('/hello', function () { return response()->json(['message' => 'Hello World']); }); [OK]

Hint: GET routes return JSON with response()->json() [OK]

Common Mistakes:

• Using POST or PUT instead of GET
• Returning plain strings instead of JSON
• Returning views in API routes

3. Given this API route in routes/api.php:

Route::post('/user', function (Illuminate\Http\Request $request) {
    return ['name' => $request->input('name'), 'age' => $request->input('age')];
});

What will be the JSON response if a POST request sends {"name": "Alice", "age": 30}?

medium

A. An error because input() is not valid

B. {"name": null, "age": null}

C. {"name": "Alice", "age": 30}

D. Empty response

Solution

1. Step 1: Understand the route and request handling

   The route accepts a POST request and reads 'name' and 'age' from the request input.

2. Step 2: Analyze the input data and response

   The POST request sends JSON with 'name' as "Alice" and 'age' as 30, so the route returns these values as JSON.

3. Final Answer:

   {"name": "Alice", "age": 30} -> Option C

4. Quick Check:

   POST input data returned as JSON = {"name": "Alice", "age": 30} [OK]

Hint: POST data accessed by input() returns JSON response [OK]

Common Mistakes:

• Assuming input() won't read JSON body
• Expecting null values if input keys missing
• Confusing GET and POST request handling

4. What is wrong with this API route definition?

Route::get('/data', function () {
    return response('Data');
});

medium

A. It should return JSON, not plain text, for API routes

B. The HTTP verb GET is not allowed in API routes

C. The route path must start with /api/

D. The closure must accept a Request parameter

Solution

1. Step 1: Check the response type for API routes

   API routes should return JSON data, but this returns plain text with response('Data').

2. Step 2: Verify HTTP verb and route path

   GET is allowed, and route paths don't need to start with /api/ because the file already scopes them.

3. Final Answer:

   It should return JSON, not plain text, for API routes -> Option A

4. Quick Check:

   API routes expect JSON responses [OK]

Hint: API routes should return JSON, not plain text [OK]

Common Mistakes:

• Thinking GET is disallowed in API routes
• Believing route paths must start with /api/
• Assuming Request parameter is mandatory

5. You want to create an API route that accepts a user ID in the URL and returns JSON with the user's name. Which of these route definitions correctly achieves this?

hard

A. Route::post('/user', function ($id) { return ['name' => 'User ' . $id]; });

B. Route::get('/user/{id}', function ($id) { return ['name' => 'User ' . $id]; });

C. Route::get('/user', function (Request $request) { return ['name' => 'User ' . $request->id]; });

D. Route::get('/user/{id}', function () { return ['name' => 'User']; });

Solution

1. Step 1: Identify route with URL parameter

   The route must accept a user ID in the URL, so it needs a parameter like {id} in the path.

2. Step 2: Check function parameters and response

   Route::get('/user/{id}', function ($id) { return ['name' => 'User ' . $id]; }); correctly uses $id parameter and returns JSON with the user's name including the ID.

3. Final Answer:

   Route::get('/user/{id}', function ($id) { return ['name' => 'User ' . $id]; }); -> Option B

4. Quick Check:

   URL param {id} passed as $id = Route::get('/user/{id}', function ($id) { return ['name' => 'User ' . $id]; }); [OK]

Hint: Use {id} in route and accept $id in closure [OK]

Common Mistakes:

• Using POST instead of GET for URL params
• Not including {id} in route path
• Not accepting $id parameter in closure