Symfony Interview Questions and Answers Web Development

Symfony PHP framework is effortless to use gratitude to its Ruby-On-As a development framework. Symfony simplifies a developer's work, as it doesn't require writing extensive codes to create web applications.

Advantages of Symfony Framework: 

1. Fast-Paced Development: Time requires fast and high-performance applications. The developer community needs the flexibility to create great applications. Symfony 2 has the ability for performance optimization of applications. It ingests less memory and authorizes developers to develop applications at a considerable speed. 
2. Flexibility: Symfony is fully adjustable to a developer's unique requirements, with independent and configurable components. Developers can easily create complicated applications with multiple functional features with their event dispatcher and dependency injector. The required functionalities can be built brick by brick and carry out the development task at their own pace. 
3. Expandable Framework: Everything is present as a bundle in Symfony. Each bundle adds unique functionality and adds to its expansion. A developer reuses a bundle in another project and shares it with the community. Bundles can be reused to change everything within Symfony without the necessity to reconfigure the complete framework. It allows changing the core itself to help expand the framework. 
4. Stable Framework: The company's developers offer support for three years, although they can provide you lifetime support on security-related issues. The company plans to furnish more stability by assuring compatibility among its minor versions. This guarantees the stability and sustainability of the application developed in any version of the framework. Moreover, it can also deliver compatibility with the public APIs for more functional advantages. 
5. Comfort & Convenience: The Framework delivers a highly functional development environment and conveys to developers the desired level of pleasure and ease. Instead of concentrating on minor functionalities, the framework facilitates developers to focus more on the core functional features of an application. This improves a developer's productivity and makes their task smooth and error-free. Symfony devices, such as the Web Debug Toolbar, bring more convenience for a developer to address errors and security-related issues. 
6. User Friendly: Symfony is an easy-to-use framework for any developer and is highly convenient for beginners and advanced users, with a host of documentation and support from the company and the community. With an acceptable level of professional support, a newbie can quickly learn the best practices of Symfony Development to help create agile and performance-driven solutions. 

Symfony Components are a collection of decoupled and reusable PHP libraries. It is open-source software that desires to quicken or speed up the creation and maintenance of web applications, substitute repetitive coding tasks, create powerful and robust applications in an enterprise context, and give developers complete control over the configuration. 

Symfony Components are decoupled libraries for PHP applications. Thousands of projects have been downloaded billions of times and are the foundation of essential PHP projects. Symfony provides components ranging from the simple feature, say file system, to advanced features, events, container technology, and dependency injection. 

Installing & Setting up the Symfony Framework 

To create a Symfony application, make sure PHP 7.1 or higher is installed using Composer. 

>> Run the command in cmd to install Symfony using Composer 

composer create-project Symfony/website-skeleton my first project 

The website is optimized for conventional web applications. If you are creating microservices, console applications, or APIs, consider using the much simpler skeleton project: 

composer create-project symfony/skeleton myFirstProject 

cd myFirstProject 

composer require symfony/web-server-bundle --dev 

Running your Symfony Application 

>> Move to new project and start the server: 

cd myFirstProject 

php bin/console server:run 

Open your browser and navigate to localhost. If everything is operating, you'll see a welcome page. 

This is a frequently asked Symfony interview question.  

Symfony is a comprehensive web framework and reusable components that are efficiently and effortlessly used in other applications and frameworks. Fabien Potencier wrote it, and its first version was released on 22 October 2005. 

The prominent Features of Symfony Framework are as below: 

1. Symfony web framework can be installed with ease 
2. It is highly scalable 
3. Symfony is an Open Source web framework 
4. It has a large and active Community. 
5. Flexible routing. 
6. The framework created is based on the MVC design pattern. 
7. It has a clean and elegant template engine. 
8. It supports easy testing and has long-term support. 
9. Online and extensive documentation is available, which helps developers to write code with ease. 

Type on the command line and use the PHP bin/console to view the installed version of the Symfony framework. 

Version history details on Symfony in

symfony/src/Symfony/Component/HttpKernel/Kernel.php file

Expect to come across this popular Symfony framework interview question.

Below is the quick synapse for Symfony 

A controller is a PHP function created. It reads data from the request object and creates and returns a response object. The response object's response can be an HTML page, JSON, XML, a file download, a redirect, a 404 error, or anything else. The Controller executes an arbitrary logic that the application needs to render a page's content. 

Yes, the Symfony framework uses a controller. A controller can be a function or a Closure and is usually a method inside a controller class: 

Example as below: 

namespace App\Controller; 
use Symfony\Component\HttpFoundation\Response; 
use Symfony\Component\Routing\Annotation\Route; 
class FirstController 
{ 
/** 
* @Route("/luckyguy/firstnumber/{max}", name="app_first_number") 
*/ 
public function number(int $max): Response 
{ 
$firstnumber = random_int(0, $max); 
return new Response( 
'<html><body>First number: '.$firstnumber.'</body></html>' 
); 
} 
} 

The symfony framework uses the php bin/console debug:router command to list the entire set of routes that we have created in our application, making use of the annotations in the controllers. 

A must-know for anyone heading into Symfony interview, this is frequently asked in Symfony framework interview questions.  

Symfony's default template engine is Twig. We can also use plain PHP code. Twig is the current and modern template engine for PHP. 

Below are the importance of the Twig template engine:

1. Fast: The overhead of regular code PHP code was reduced to a bare minimum as Twig helps to compile templates down to plain optimized PHP code. 
2. Secure: Twig as a template language is used for applications where users can modify the template design. It has a sandbox mode to reckon untrusted template code. 
3. Flexible: Twig allows the developer to specify custom tags and filters and create its DSL as is authorized by flexible lexer and parser power twig. 

Cache adapters are the actual caching means to store the data in the filesystem, in a database, etc.

Symfony has five cache adapters are as follows: 

1. File system cache adapter 
2. Array cache adapter 
3. APCu cache adapter 
4. PHP files cache adapter 
5. Redis cache adapter 

Symfony application commences with three environments: dev, prod, and test. Each environment represents a mode to accomplish the same codebase with a distinct configuration. Each environment loads its configuration files. These different files are organized by environment: 

1. for the dev environment: config/packages/dev/ 
2. for the prod environment: config/packages/prod/ 
3. for the test environment: config/packages/test/ 

All environments share a large base of standard configurations. This configuration is put in files directly in the config/packages/ directory. 

To find the version of Symfony, run the following commands in the command prompt 

$ php bin/console --version 
Symfony 5.1.1 (env: prod, debug: false) 
$ php app/console --version 
Symfony version 2.4.1 - app/dev/debug 
$ php ./symfony --version 
symfony version 1.4.21-punkave (/var/www/p/releases/20200504161617/lib/vendor/symfony/lib) 

The version can be found within the project files. 

vendor/symfony/http-kernel/Kernel.php 
vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Kernel.php
 
const VERSION = '5.0.4'; 

Version can also found by using the following code: 

$request = $this->container->get(‘request’); 
$currentRouteName = $request->get(‘_route’); 

A Symfony controller redirects and forwards core services to render templates. Symfony controllers can be used for various basic tasks. 

Following are the general rules for creating a method within the Symfony controller. 

1. Action methods can be public. 
2. Controller methods should be short. Refactor it; if it is long. 
3. Suffix "action" within action methods 
4. A valid response object should return from action methods. 

First you need to add the class use ApiPlatform\Core\Annotation\ApiResource; and then we add the corresponding annotation, which creates some routes of the crud type or any route that we can use 

#[ApiResource(routePrefix: '/')] 

As a rule, we add these annotations in the entity class.

One of the most frequently posed Symfony interview questions, be ready for it.  

We have several ways to protect access to our routes, the first is in the security.yaml file and the second is using the method $this->denyAccessUnlessGranted('ROLE_ADMIN'); in the method that we want to protect.

It's no surprise that this one pops up often in Symfony interview questions.  

The index method uses the get method by default, and we will use it to obtain a data 

#[Route('/', name: 'user_index', methods: ['GET'])] 
public function index(UserRepository $userRepository): Response 
{ 
//Code should be written within this function 
} 

The new method uses the post method, and we use it to create data 

#[Route('/new', name: 'user_new', methods: ['POST'])] 
public function new(Request $request, EntityManagerInterface $entityManager): Response 
{ 
//Code should be written within this function 
} 

The show method uses the get method, and we will use it to obtain data through a parameter. 

#[Route('/{id}', name: 'user_show', methods: ['GET'])] 
public function show(int $id): Response 
{ 
//Code should be written within this function 
} 

The edit method uses the put or patch method, and we will use it to update a data 

 #[Route('/{id}/edit', name: 'user_edit', methods: ['PUT', 'PATCH'])] 
public function edit(Request $request, User $user, EntityManagerInterface $entityManager): Response 
{ 
//Code should be written within this function 
} 

The delete method uses the delete method, and we will use it to delete data 

#[Route('/{id}', name: 'user_delete', methods: ['Delete'])] 
public function delete(User $user): Response 
{ 
//Code should be written within this function 
} 

We have several ways to protect access to our routes. The first is in security.yaml file and the second is using the method $this->denyAccessUnlessGranted('ROLE_ADMIN'); in the method that we want to protect.

A common in Symfony interview questions, don't miss this one.  

Bundles in Symfony are similar to plugins or packages in other CMS frameworks. Everything is a bundle, from core framework components to your writing code in Symfony. The bundle authorizes using pre-built features packed in third-party bundles or creating and distributing own bundles. 

There are two types of bundles 

1. Application-specific bundles: Used to build your application. 
2. Reusable bundles: Shared across multiple projects. 

DoctrineFixturesBundle is the bundle that should be used when working with a lot of test data which can be combined with the faker library. 

First, we use the class at the top of the controller use App\Repository\UserRepository; 

Then we inject the class into the controller 

#[Route('/', name: 'user_index', methods: ['GET'])] 
public function index(UserRepository $userRepository): Response 
{ 
$users = $userRepository->findAll(); 
return $this->json($users); 
} 

Where we can access its methods and properties.

A staple in Symfony interview questions, be prepared to answer this one.  

The routing configuration specifies the action to run for each incoming URL. It also provides other useful features, like generating SEO-friendly.

The routing configuration files of Symfony are written with YAML, XML, and PHP technologies. app/config/routing.yml is the default routing configuration file in Symfony

Use native attributes in PHP 8 to configure routes, and On PHP 7, use annotations instead, provided by the Doctrine Annotations library. 

By default, Symfony utilizes a twig as a template engine. Twig is a flexible, fast, secure, and open-source template engine for PHP and originates its syntax from Jinja and Django templates. It is licensed under a BSD License and maintained by Fabien Potencier. 

A modern template engine as a twig for PHP has the following features. 

1. Fast: It compiles to plain optimized PHP code, reducing the overhead compared to regular PHP to a minimum. 
2. Secure: It has a sandbox way to assess untrusted template code. It can be used as a template language for applications where users can modify the template design. 
3. Flexible: It is powered by a flexible lexer and parser. Developers can define their custom tags and filters and create DSL. 

Annotations are utilized for configuration validation and mapping Doctrine information in the Symfony framework. They are easy and convenient to use. We have two different bundles SensioFrameworkExtraBundle and JMSSecurityExtraBundle, which provide better support for annotations in the standard edition of Symfony. Using bundles, annotations can be used for controller configuration, routing, cache, security, template, etc. 

Example with Annotations 

In app/config/routing.yml: 

blog_front: 
resource: "@BlogFrontBundle/Controller/" 
type: annotation 
prefix: / 

Filenamen: src/Blog/FrontBundle/Controller/HomeTestController.php: 

<?php 
namespace Blog\FrontBundle\Controller; 
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route; 
class HomeController 
{ 
/** 
* @Route("/", name="blog_home_index_Test") 
*/ 
public function indexAction() { /* ... */ } 
} 

In symfony version 5 paths use the sign @ 

@Route("/", name="user_index", methods={"GET"}) 

In symfony version 6 paths use the sign # 

#[Route('/', name: 'user_index', methods: ['GET'])] 

Symfony is a notable PHP framework for web and support applications and many reusable PHP segments that any developer can reuse. Multiple applications use Symfony for their development. Well-known PHP ventures include Trivago, Typeform, BlaBlaCar, Statista, Deezer, Spotify, Shopware, Magento, Drupal, Joomla, Wikimedia, Matomo, phpBB, ownCloud use Symfony framework application.

Symfony is a convention-based framework. The Coding Standards document illustrates the coding norms for the Symfony projects and the internal and third-party bundles. It defines coding standards and conventions used in the core framework to construct or make it more uniform and predictable.

This is frequently asked in PHP framework interview questions.  

Laravel is an open-source framework. It observes a model-view-controller design pattern and uses components of different frameworks to create a web application. It has features of PHP frameworks like Yii, CodeIgniter, or Ruby on Rails. It is famous for developing simple applications and reducing the development time framework. 

Symfony is an open-source PHP project like Propel, Doctrine, PHPUnit, Twig, and Swift Mailer. Symfony has components like Symfony YAML, Symfony Event Dispatcher, Symfony Dependency Injector, and Symfony Templating. Symfony has risen as a more reliable and mature framework. It is used for complex enterprise projects. 

Symfony is the best option because of the following reasons 

1. If we are creating a complex enterprise application symfony is the best option as it is very scalable, maintainable, and well structured. 
2. Carrying over a migration of a big long-term project as Symfony will have release in quick sessions for the next six years, so it’s less likely that there will be any surprises. 

_route was always meant for debugging.

In this case, use 

$router = $this->get("router"); 
$route = $router->match($this->getRequest()->getPathInfo()); 
var_dump($route['_route']); 

OR 

class MyController extends Controller 
{ 
public function myAction($_route) 
{ 
var_dump($_route); 
} 
} 

Expect to come across this popular question in Symfony interview questions.  

In Symfony, an AccessDeniedException can be thrown when access is denied to the user. Symfony will handle this exception. 

Symphony denies access to the user for the below reasons

1. The user is not authenticated and is redirected to the login page, or there is 401 Unauthorized response 
2. The user is authenticated but doesn't have required permissions ; a 403 Forbidden response is induced. 

We can pass parameters in our routes and perform a check in case the element does not exist in the query and throw an exception.

public function show(int $id): Response 

{ 
$user = $userRepository->find($id); 
if (!$user) { 
throw $this->createNotFoundException( 
'No user found for id '.$id 
); 
}
} 

It's no surprise that this one pops up often in Symfony interview questions for experienced.  

In Symfony session class is used to configure sessions. This session class can serve all functions of PHP sessions.

The examples below will provide an update on creating and removing sessions in Symfony. 

Creating Session in Symfony 

$session = new Session();
$session->start();

Setting Session in Symfony 

$session->set('user_id', 200);

Getting session in Symfony 

$session->get('user_id');

Removing / Destroying session in Symfony 

$session->remove('user_id');

A common in Symfony interview questions, don't miss this one.  

Descriptors are objects in Symfony that can be used to generate documentation and information on the console Apps.

Form Helper Function 

Form helper functions are an example of twig functions that help to create forms easily. 

form_start 

HTML form tag points to a valid action, route, or URL. 

Syntax − 

{{ form_start(form, {'attr': {'id': 'form_person_edit'}}) }}

form_end 

Closes the HTML form tag after using form_start.

Syntax− 

{{ form_end(form) }}

textarea 

Returns a textarea tag wrapped with an inline rich-text JavaScript editor. 

checkbox 

XHTML compliant input tag with type=“checkbox”.

Syntax− 

echo checkbox_tag('choice[]', 1);
echo checkbox_tag('choice[]', 2);
echo checkbox_tag('choice[]', 3);
echo checkbox_tag('choice[]', 4);

input_password_tag 

An XHTML compliant input tag with type = “password”.

Syntax− 

echo input_password_tag('password');
echo input_password_tag('password_confirm'); 

input_tag 

An XHTML compliant input tag with type = “text”.

Syntax- 

echo input_tag('name');

label 

Returns with the specified parameter. 

radiobutton 

Ab XHTML compliant input tag with type = “radio”. 

Syntax- 

echo ' Yes '.radiobutton_tag(‘true’, 1);
echo ' No '.radiobutton_tag(‘false’, 0);

reset_tag 

An XHTML compliant input tag with type = “reset”.

Syntax- 

echo reset_tag('Start Over');

select 

A select tag populated with all the countries in the world. 

Syntax− 

echo select_tag('url', options_for_select($url_list), array('onChange' =>'Javascript:this.form.submit();'));

submit 

An XHTML input tag with type = “submit”.

Syntax− 

echo submit_tag('Update Next Record'); 

Step 1: Create a Symfony Application 

symfony new formsampleTest 

Entities are created in “src/AppBundle/Entity/“ directory. 

Step 2: Creating an Entity 

Create the file “StudentFormTest.php” in the “src/AppBundle/Entity/” directory.

StudentFormTest.php 
<?php
namespace AppBundle\Entity;
class StudentForm {
private $studentName;
private $studentId;
public $password;
private $address;
public function getStudentName() {
return $this->studentName;
}
public function setStudentName($studentName) {
$this->studentName = $studentName;
}
public function getStudentId() {
return $this->studentId;
}
public function setStudentId($studentid) {
$this->studentid = $studentid;
} 
public function getAddress() {
return $this->address;
}
public function setAddress($address) {
$this->address = $address;
}
public function getEmail() {
return $this->email;
}
public function setEmail($email) {
$this->email = $email;
}
public function getMarks() {
return $this->marks;
}
public function setMarks($marks) {
$this->marks = $marks;
}
}

Step 3: Create StudentController 

Create “StudentController.php” File in directory “src/AppBundle/Controller” 

StudentController.php 
<?php
namespace AppBundle\Controller;
use AppBundle\Entity\StudentForm;
use AppBundle\Form\FormValidationType;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Request;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Form\Extension\Core\Type\TextType;
use Symfony\Component\Form\Extension\Core\Type\DateType;
use Symfony\Component\Form\Extension\Core\Type\SubmitType;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
use Symfony\Component\Form\Extension\Core\Type\PasswordType;
use Symfony\Component\Form\Extension\Core\Type\RangeType;
use Symfony\Component\Form\Extension\Core\Type\EmailType;
use Symfony\Component\Form\Extension\Core\Type\CheckboxType;
use Symfony\Component\Form\Extension\Core\Type\ButtonType;
use Symfony\Component\Form\Extension\Core\Type\TextareaType;
use Symfony\Component\Form\Extension\Core\Type\PercentType;
use Symfony\Component\Form\Extension\Core\Type\RepeatedType;
class StudentController extends Controller {
/**
* @Route("/student/new")
*/
public function newAction(Request $request) {
$stud = new StudentForm();
$form = $this->createFormBuilder($stud)
->add('studentName', TextType::class) 
->add('studentId', TextType::class)
->add('password', RepeatedType::class, array(
'type' => PasswordType::class,
'invalid_message' => 'The password fields
must match.', 'options' => array('attr' => array('class' => 'password-field')),
'required' => true, 'first_options' => array('label' => 'Password'),
'second_options' => array('label' => 'Re-enter'),
))
->add('address', TextareaType::class)
))
->add('save', SubmitType::class, array('label' => 'Submit'))
->getForm();
return $this->render('student/new.html.twig', array(
'form' => $form->createView(),
));
}
}

Step 4: Render the View 

create “new.html.twig” file in “app/Resources/views/student/“, directory 

{% extends 'base.html.twig' %}
{% block stylesheets %}
<style>
#simpleform {
width:600px;
border:2px solid grey;
padding:14px;
}
#simpleform label {
font-size:14px;
float:left;
width:300px;
text-align:right;
display:block;
}
#simpleform span {
font-size:11px;
color:grey;
width:100px;
text-align:right;
display:block;
}
#simpleform input {
border:1px solid grey;
font-family:verdana;
font-size:14px; 
color:light blue;
height:24px;
width:250px;
margin: 0 0 10px 10px;
}
#simpleform textarea {
border:1px solid grey;
font-family:verdana;
font-size:14px;
color:light blue;
height:120px;
width:250px;
margin: 0 0 20px 10px;
}
#simpleform select {
margin: 0 0 20px 10px;
}
#simpleform button {
clear:both;
margin-left:250px;
background: grey;
color:#FFFFFF;
border:solid 1px #666666;
font-size:16px;
}
</style>
{% endblock %}
{% block body %}
<h3>Student details:</h3>
<div id="simpleform">
{{ form_start(form) }}
{{ form_widget(form) }}
{{ form_end(form) }}
</div>
{% endblock %}

One of the most frequently posed Symfony Framework interview questions, be ready for it.  

It is necessary to use the render method which accepts the associated view as a parameter, which by convention creates a folder followed by the file with the extension .twig 

return $this->render('user/index.html.twig', [ 
'users' => $customers, 
]); 

To clear the cache in Symfony, use the cache:pool:clear command. This command will help to delete all data from the project storage directory.

Symfony possesses three cache clearers: 

1. global_clearer 
2. system_clearer 
3. app_clearer

A staple in Symfony interview questions for experienced, be prepared to answer this one.  

This is a regular feature in Symfony interview questions, be ready to tackle it.  

In Symfony, Request parameter can be extracted by using following methods: 

$request = $this->container->get(‘request’); 
$name=$request->query->get(‘name’); 

Following are the various web servers supported by Symfony. 

1. WAMP (Windows) 
2. LAMP (Linux) 
3. XAMP (Multi-platform) 
4. MAMP (Macintosh) 
5. Nginx (Multi-platform) 
6. Microsoft IIS (Windows) 
7. PHP built-in web server 

The Serializer component turns objects into a specific format (XML, JSON, YAML, ...). 

The Serializer component follows the following schema as below: 

An array is an intermediate between objects and serialized contents.

Encoders will deal with turning specific formats into arrays and vice versa.

The serialization component can help develop tools to serialize and deserialize your objects. 

We can change the data type object, array to another data type like json or xml using the class use Symfony\Component\Serializer\Serializer; 

$users = $userRepository->findAll(); 
$jsonContent = $serializer->serialize($users, 'json'); 

And to return it to the previous data type, we do the opposite with the deserialize method 

$jsonContent = $serializer->deserialize($users, 'json'); 

This is a regular feature in Symfony interview questions, be ready to tackle it.