Laravel Interview Questions

Introduction
 Laravel is an open-source PHP web framework created by Taylor Otwell, who began the project in 2011. Laravel follows the MVC (Model-View-Controller) architectural pattern, which helps in organizing and managing complex web applications efficiently. In the MVC pattern, the flow of the application starts from the controller, which handles user input and interests with a model to fetch or update data. The data is then presented to the user through the view. 

1. What is Artisan?
Artisan is a command line tool or interface for Laravel that helps the developer for building applications, which helps in making the production process fast and easy. 

Artisan is a powerful command-line tool included with Laravel that aids developers in building applications efficiently and effectively. It significantly speeds up the development process by providing a suite of commands that automate common tasks and streamline workflow.

Artisan allows developers to generate boilerplate quickly. with simple commands, you can create models, controllers, migrations, seeders, and many more. This reduces the amount of manual coding required and ensures consistency across the application.

 2. What are the advantages of using Laravel?

3. What is the composer?
Composer is a dependency manager for PHP. It simplifies the process of managing and installing the libraries and packages in the PHP project. It automatically installs the libraries and dependencies your project needs.

4. What is Middleware?
Middleware provides a convenient mechanism for inspecting and filtering HTTP requests entering your application. It acts as an intermediary that processes requests before they reach your application's core logic, allowing you to perform various tasks such as authentication, logging, and modifying requests or responses. 

You can create middleware in the Laravel application by executing the following command:

php artisan make:middleware RoleMiddleware

There are three types of middleware:
1. Global Middleware: These run on every HTTP request to your application.
2. Route Middleware: These are assigned to specific routes or groups of routes.
3. Middleware Groups: These are groups of middleware that can be applied to routes or controllers as a bundle.

4. What is Laravel Query Builder?
The Laravel Database Query Builder offers an easy interface for crafting and executing database queries. It supports all common database operations and works seamlessly with all supported database systems. By utilizing PDO parameter binding, It protects your application against SQL injection attacks, eliminating the need to manually sanitize strings before inserting them into the database. Query builder is faster than Eloquent ORM.
Example:  Basic illustrations of how to select/insert/update/delete data from a "users" table. 

use Illuminate\Support\Facades\DB;

$users = DB::table('users')->get();
$users = DB::table('users)->insert(['name' => 'John Doe', 'email' => 'johndoe@example.com']);
$users = DB::table('users)->where('id', 1)->update(['name' => 'James']);
$users = DB::table('users)->where('id', 1)->delete();

5. What is Laravel Eloquent ORM?
Laravel, along with Eloquent Objet-Relational Mapper(ORM), provides an easy and intuitive way to communicate with your database. Eloquent ORM allows you to interact with your database using an expressive syntax and provides built-in model relationships to help you manage and query related data effortlessly.

Eloquent supports various types of relationships, such as one-to-one, one-to-many, many-to-many, and polymorphic relationships, making it easy to work with related data.
 
6. What is Migration?
Migrations in Laravel act as version control for your database schema. They allow you to define and track changes to your database structure,  such as creating a new table, altering existing tables, adding or modifying columns, and seeding the database with initial data.

php artisan make:migration create_users_table

This command generates a migration file with a timestamp prefix in the database/migrations directory. The timestamp helps Laravel determine the order in which migrations should be run.

7. Which database is supported in Laravel?
Laravel supports a variety of database systems, including:
MYSQL: A popular open-source relational database management system.
PostgreSQL: An advanced, enterprise-class open-source relational database.
SQLite: A Lightweight, file-based relational database management system.
SQL Server: Microsoft's relational database management system.

8. How to soft delete?
Laravel allows you to make a record as deleted without actually removing it from the database. The data can be restored later if needed. First, you need to include the SoftDeletes trait in your Eloquent model. 

9. Define Environment Variables?
Environment variables are global variables that define key configuration settings that can be accessed throughout the application. these variables are typically stored in the .env file, which allows for easy management and configuration of different environments (e.g., local, production).
You can use the env helper function for example, env('APP_NAME', 'CompanionGuru');    

9. What is a Seeder in Laravel?
A seeder in Laravel is used to insert default or simple records into the database automatically. This is particularly useful during the development and testing to populate the database with data quickly. By running seeder commands, you can insert data into your database tables.
Use the Artisan command to generate a new seeder class.

php artisan make:seeder UsersTableSeeder

This command creates a new seeder file in the database/seeders directory.

10. How to print the current Laravel version?
There are several ways to print the current version of your Laravel application.

Using the Artisan command:

php artisan --version

Using the app() Helper:

echo app()->version();

Using the App Facade:

echo \App::VERSION();

11. Command to list all available Artisan commands in Laravel.
To see a list of all available Artisan commands, you can use the following command:

php artisan list

12. List of some examples of Laravel packages.
There are many packages available in Laravel. Below are a few examples:
Laravel Debugbar: A developer toolbar for debugging purposes.
Socialite: Facilitates login via social networks (e.g. Google, Facebook).
Intervention/Image: A library for image handling and manipulation.
Spatie/laravel-medialibrary: Associates various types of files with Eloquent models.
Spatie/Image-optimizer: Optimizes JPG, PNG, SVG, and GIF files by running them through a series of image optimization tools.
Maatwebsite/Excel: Used for importing and exporting data to and from Excel files.

13. How to clear the Cache in Laravel?
You can clear various caches in Laravel using the following artisan commands:

• Clear and cache the routes: php artisan route:cache
• Clear and cache the configuration: php artisan config:cache 
• Clear the application cache: php artisan cache:clear
• Clear the complied views: php artisan view:clear
• Clear all the caches: php artisan optimize:clear

Clear cache without Artisan commands like:

Artisan::call('route:clear');
Artisan::call('optimize:clear');

14. What is the use of dd() function in Laravel?
The dd() function stands for “Dump and Die”. It is used to output the contents of a variable (or multiple variables)  for debugging purposes and then immediately stops the execution of the script. This function is particularly useful for inspecting variables during development.
The dump() function, outputs the data but allows the script to continue execution.
 
15. What is @iclude and @extends in Laravel?
The @include directive in Laravel blade templates is similar to the PHP include function. It allows you to include the content of one Blade view file into another. This is useful for including reusable components like header, footer, or any other partials.
The @extends directory is used for template inheritance. It allows a Blade view to extend a Layout view, Inheriting its structure and defining sections that will populate specific parts of the layout.

16. What is CSRF token?
A CSRF (Cross-Site Request Forgery) token is a unique security measure used to protect web applications from unauthorized or malicious requests. It works by generating a unique token for each session or user request and embedding this token forms or requests. When the request is submitted, the server verifies that the token matches, ensuring that the request is coming from a legitimate source.

17. How to disable CSRF protection for specific routes?
If you need to disable CSRF protection for specific routes, you can do so by adding those routes to the $except property in the VerifyCsrfToken.php file, which is located in the app/Http/Middleware directory.

18. What are the available router methods in Laravel?
Laravel provides several HTTP routing methods to define routes for different types of requests. 
GET: Retrieve data from the server.
POST: Submit the data to the server.
PUT: Update existing data on the server.
PATCH: Partially update existing data on the server.
DELETE: Remove data from the server.
OPTIONS: Describe the communication options for the target source.
ANY: Match all request methods.
MATCH: Match specific HTTP methods.
REDIRECT: Redirect one URL to another.
VIEW: Return a view directly from the route.
 
19. What is a Route in Laravel?
A route in Laravel is a mechanism for defining URL patterns and their corresponding actions or controllers in your application. Routes are essential for directing incoming HTTP requests to the appropriate logic in your application, ensuring that users can access the right resources and functionalities.

Routes are typically defined in the routes/web.php file for web routes and routes/api.php for API routes. Each route is defined using a routing method corresponding to the HTTP verb.

20. What are the main Routing files?
Laravel uses different routing files to organize and manage the routes for various parts of your application. The main routing files are:
1. web.php: Handle web routes associated with views, sessions, and cookies.
2. api.php: Manage stateless routes for APIs suitable for web and mobile applications.
3. console.php: Define routes for custom Artisan commands.  

21. What is a Resource Controller?
A resource controller is a type of controller that automatically generates predefined routes and their corresponding methods for performing CRUD operations, instead of manually defining routes for each action (like index, create, store, show, edit, update, and destroy).

Example: 

Route::resource('posts', PostController::class);

Generating Routes:

//URLs
url(route('posts.index'));
url(route('posts.show', ['post' => $post->id ])); //Specific routes

//Redirecting
return redirect()->route('posts.index');

21. Laravel database : migrate:refresh  VS migrate:fresh?
migrate:refresh:
The migrate:refresh command rolls back all the existing migrations and then re-runs them, essentially recreating the database schema from scratch. 
- The migrate:refresh command first calls the down methods of all your existing migrations, effectively rolling back all changes to your database.
- After rolling back, it executes the up methods for your migrations,  reapplying all changes.
- Rolls back and re-runs migrations.
- Completely wipes the database, so all the data is lost. It's useful when you need a blank slate.
Example:

php artisan migrate:refresh 

migrate:fresh:
The migrate:fresh command, drops all the tables from the database and then runs the up  methods from your migrations. This command completely wipes the database clean, removing all the tables and data, before applying migrations.
 Example:

php artisan migrate:fresh

• Typically, it is faster, as it directly drops and then recreates tables without the rollback step.

21. What is the Foreign Key & How can it be Defined in Laravel? 
 A  foreign key is a field (or collection of fields) in one table that uniquely identifies a row in another table. referential integrity between tables. 
Example: 
We'll create a products table with a foreign key that references the categories table.

public function up(): void
{
	Schema::create('products', function (Blueprint $table) {
		$table->id(); // Primary key (auto-incrementing)
		$table->string('name'); // Product name
		$table->integer('price'); // Product price
		$table->unsignedBigInteger('category_id'); // Foreign key column

		// Defining the foreign key constraint
		$table->foreign('category_id')
			  ->references('id')
			  ->on('categories')
			  ->onUpdate('cascade')  // Cascade updates
			  ->onDelete('cascade'); // Cascade deletes

		$table->timestamps(); // Timestamps for created_at and updated_at
});

22. What is the purpose of the Artisan command line tool? 
 Command Line tool for assisting the developer in creating applications, such as creating controller, model, migrations, and more. It reduces manual work.

• Controller: (Creates a controller file)

php artisan make:controller UserController

• Model: (Creates a model file)

php artisan make:model User

Generate a model named User. Use -m to include a migration: 

php artisan make:model User -m

• Migration: (Create a migration file for database schema changes)

php artisan make:migration create_users_table

• Seeder: (Create a seeder file for database  data population)

php artisan make:seeder UserSeeder

• Factory: (Create a factory file for generating test data)

php artisan make:factory UserFactory

• Policy: (Create a policy file to handle authorization logic)

php artisan make:policy UserPolicy

• Command: (Create a new Artisan command class named CustomCommand.php  in app/console/commands )

php artisan make:command CustomCommand

23. What is Accessor and Mutator? 
 Accessor : An accessor transforms an Eloquent attribute value when it is accessed (retrieved).

public function getNameAttribute($value){
	return ucwords($value);
}

Mutator : A mutator transforms an eloquent attribute value when it is set.

public function setPasswordAttribute($value){
	$this->attributes['password'] = bcrypt($value);
}

24. What is a model Observer? 
 A Laravel observer is a software design pattern that allows you to various events or operations that occur on a model. An observer class is an object that can listen to events such as creating, created, updating, updated, deleting, deleted, and more. improving code organization and maintainability by keeping your models clean.

//Example (Creating)
public function created(Post $post){
	$post->slug = Str::slug($post->title);
	$post->save();
}

25. What is the default Laravel session timeout? 
 In Laravel default session timeout is 120 minutes (2 hours). This is specified in the configuration file config/sesssion.php under the lifetime key. ('lifetime' => 120).
 26. What is caching? 
 Caching is a mechanism used to store the data in temporary to reduce server load, enhance performance, and speed up data retrival. By reducing the need to repeatedly fetch data from original  source (e.g, a database or API), and accelerates response times.