PHP Developer Interview Questions
Powering a significant portion of the web, PHP remains an essential tool for web developers. To assist in finding the top talent in PHP development, this article collates a set of probing interview questions. Gauge a candidate's ability to craft dynamic, secure, and efficient web applications and services using this versatile scripting language.
What is PHP and its primary use?
Answer: PHP stands for Hypertext Preprocessor. It is a server-side scripting language primarily used for web development to create dynamic web pages.
2.
How does PHP differ from languages like JavaScript?
Answer: PHP is a server-side scripting language, executing on the server and sending HTML to the client. In contrast, JavaScript is client-side, running in the browser.
3.
Describe the difference between "echo" and "print" in PHP.
Answer: Both are used for output. However, "echo" can take multiple parameters, whereas "print" accepts only one and returns 1, thus behaving like a function.
4.
What are session variables, and why are they useful?
Answer: Session variables maintain user data across multiple pages during user interactions. They provide continuity and are useful for things like user authentication.
5.
Can you explain the concept of PHP "super globals"?
Answer: These are built-in global arrays in PHP, like $_GET, $_POST, and $_SESSION, that provide data from various sources (e.g., form input) accessible throughout a script.
6.
How is data sent in a POST request?
Answer: Data is sent in the request body, making POST requests suited for sending large amounts of data, especially of sensitive nature.
7.
What is PDO and why is it significant?
Answer: PDO (PHP Data Objects) provides a consistent way to access databases, allowing developers to use different databases with the same functions and methods.
8.
How can one prevent SQL injections in PHP?
Answer: By using prepared statements and parameterized queries, often available through PDO or MySQLi.
9.
What is the "ternary operator" in PHP?
Answer: It's a shorthand for if-else statements, used like: $x = (expression) ? value_if_true : value_if_false.
10.
Describe the use of isset() in PHP.
Answer: isset() determines if a variable is declared and has a value other than NULL. It's often used to check if form input exists.
11.
What does include and require do?
Answer: Both are used to include a file within another PHP script. The difference lies in error handling; require will produce a fatal error and halt script execution if the file isn't found, while include only produces a warning.
12.
How are cookies set in PHP?
Answer: Using the setcookie() function, which sends a HTTP cookie to the client.
13.
Explain OOP in the context of PHP.
Answer: PHP supports object-oriented programming (OOP), allowing developers to define classes, create objects, and use principles like inheritance, polymorphism, and encapsulation.
14.
What is namespacing in PHP and why is it useful?
Answer: Namespacing allows for better organization by encapsulating items. It helps prevent naming collisions in larger applications or when using third-party libraries.
15.
How can PHP handle file uploads?
Answer: Using the $_FILES super global and functions like move_uploaded_file(). Proper validation and security checks should be applied during uploads.
16.
Explain the __construct() method in PHP.
Answer: It's a constructor method invoked when an object of a class is created. Useful for any initialization an object may need upon creation.
17.
Describe the difference between "GET" and "POST" methods in PHP.
Answer: "GET" sends data via URL and has length restrictions, while "POST" sends data in the request body and is more secure and suitable for larger data.
18.
How do you start and destroy a session in PHP?
Answer: Using session_start() to start and session_destroy() to destroy a session.
19.
Explain the significance of the header() function in PHP.
Answer: It's used to send raw HTTP headers. For instance, it can be used for redirection or to set content type.
20.
What are "magic methods" in PHP?
Answer: These are methods with specific names, starting with two underscores (e.g., __construct(), __destruct()) that are triggered under particular circumstances.
21.
What is the MVC pattern and its relevance in PHP frameworks?
Answer: Model-View-Controller (MVC) separates an application into three interconnected components. Many PHP frameworks, like Laravel and CodeIgniter, employ this pattern for organized and modular development.
22.
Explain dependency injection in PHP.
Answer: Dependency injection provides objects with their dependencies. It promotes decoupling, making the system more modular and testable.
23.
What is composer in PHP?
Answer: Composer is a dependency management tool in PHP, allowing developers to declare and manage libraries on a per-project basis.
24.
How does "late static binding" work in PHP?
Answer: Introduced in PHP 5.3.0, it allows for referencing the called class in a context of static inheritance.
25.
What's the significance of PSR standards in PHP?
Answer: PSR standards, proposed by the PHP-FIG group, ensure coding standardization and interoperability of shared PHP code. Following PSR standards makes collaborative development smoother.
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