# Modern PHP (8.1+) (Symfony)

> Enums, readonly properties, attributes, promoted properties, named arguments, union types, strict typing, match expression

- 20 interview questions
- Junior
- [Interview Questions: Symfony](https://sharpskill.dev/en/technologies/symfony/interview-questions.md)

## 1. What is the correct syntax to declare an enumeration (enum) in PHP 8.1+?

**Answer**

In PHP 8.1+, enumerations are declared using the enum keyword followed by the name and possible cases within braces. Enums allow defining a type with a finite set of possible values, which improves type safety and makes code more expressive. Backed enums can have associated string or int values.

## 2. What is a backed enum in PHP 8.1+?

**Answer**

A backed enum is an enumeration where each case is associated with a scalar value (string or int). This value enables serialization and database storage. The syntax uses a colon after the enum name to specify the backing type, then each case receives a value with the equals sign.

## 3. How to declare a readonly property in PHP 8.1+?

**Answer**

The readonly modifier is placed before the property type. A readonly property can only be initialized once, either in the declaration or in the constructor. Once set, its value cannot be changed, which guarantees the immutability of that property.

## 17 more questions available

- What is the main constraint of a readonly property in PHP 8.1+?
- What is constructor property promotion in PHP 8.0+?

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## Other Symfony interview topics

- [Symfony Basics](https://sharpskill.dev/en/technologies/symfony/interview-questions/symfony-basics.md): 25 questions, Junior
- [Routing & Controllers](https://sharpskill.dev/en/technologies/symfony/interview-questions/routing-controllers.md): 20 questions, Junior
- [Twig & Templates](https://sharpskill.dev/en/technologies/symfony/interview-questions/twig-templates.md): 20 questions, Junior
- [Doctrine ORM Basics](https://sharpskill.dev/en/technologies/symfony/interview-questions/doctrine-orm-basics.md): 25 questions, Junior
- [Symfony Forms](https://sharpskill.dev/en/technologies/symfony/interview-questions/forms.md): 22 questions, Junior
- [Data Validation](https://sharpskill.dev/en/technologies/symfony/interview-questions/validation.md): 18 questions, Junior
- [Dependency Injection & Services](https://sharpskill.dev/en/technologies/symfony/interview-questions/dependency-injection.md): 24 questions, Mid-Level
- [Security & Authentication](https://sharpskill.dev/en/technologies/symfony/interview-questions/security-authentication.md): 26 questions, Mid-Level
- [Doctrine Advanced](https://sharpskill.dev/en/technologies/symfony/interview-questions/doctrine-advanced.md): 24 questions, Mid-Level
- [API Platform](https://sharpskill.dev/en/technologies/symfony/interview-questions/api-platform.md): 22 questions, Mid-Level
- [Serializer Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/serializer.md): 20 questions, Mid-Level
- [Events & Event Subscribers](https://sharpskill.dev/en/technologies/symfony/interview-questions/events-subscribers.md): 20 questions, Mid-Level
- [Console & Commands](https://sharpskill.dev/en/technologies/symfony/interview-questions/console-commands.md): 18 questions, Mid-Level
- [Messenger Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/messenger.md): 22 questions, Mid-Level
- [HTTP Client](https://sharpskill.dev/en/technologies/symfony/interview-questions/http-client.md): 18 questions, Mid-Level
- [Cache & Performance](https://sharpskill.dev/en/technologies/symfony/interview-questions/cache.md): 20 questions, Mid-Level
- [Workflow Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/workflow.md): 18 questions, Mid-Level
- [Testing Symfony](https://sharpskill.dev/en/technologies/symfony/interview-questions/testing.md): 22 questions, Mid-Level
- [Mailer Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/mailer.md): 16 questions, Mid-Level
- [Translations & i18n](https://sharpskill.dev/en/technologies/symfony/interview-questions/translations.md): 16 questions, Mid-Level
- [EasyAdmin Bundle](https://sharpskill.dev/en/technologies/symfony/interview-questions/easyadmin.md): 18 questions, Mid-Level
- [Symfony Architecture](https://sharpskill.dev/en/technologies/symfony/interview-questions/architecture-patterns.md): 24 questions, Senior
- [Performance & Optimization](https://sharpskill.dev/en/technologies/symfony/interview-questions/performance-optimization.md): 22 questions, Senior
- [Security Advanced](https://sharpskill.dev/en/technologies/symfony/interview-questions/security-advanced.md): 22 questions, Senior
- [Custom Bundles](https://sharpskill.dev/en/technologies/symfony/interview-questions/custom-bundles.md): 20 questions, Senior
- [Microservices with Symfony](https://sharpskill.dev/en/technologies/symfony/interview-questions/microservices.md): 22 questions, Senior
- [Real-time & WebSockets](https://sharpskill.dev/en/technologies/symfony/interview-questions/real-time.md): 18 questions, Senior
- [Deployment & DevOps](https://sharpskill.dev/en/technologies/symfony/interview-questions/deployment-devops.md): 20 questions, Senior

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