Common Interview Questions for PHP Jobs and How to Answer Them

 PHP (Hypertext Preprocessor) remains one of the most widely used server-side scripting languages for web development. If you're preparing for a PHP job interview, you should be ready to answer a mix of technical and conceptual questions. Below are some of the most frequently asked PHP interview questions and tips on how to answer them effectively.

1. What is PHP?

Answer:
PHP is a widely-used, open-source server-side scripting language designed for web development. It can be embedded into HTML and is often used to create dynamic web pages and applications. PHP scripts are executed on the server, and the output is sent to the client’s browser.

2. What are the differences between PHP 5 and PHP 7?

Answer:

  • Performance: PHP 7 is almost twice as fast as PHP 5 due to the new Zend Engine.
  • Error Handling: PHP 7 introduced throwable exceptions (Error class) for better error management.
  • Type Declarations: PHP 7 introduced scalar type hints and return type declarations.
  • New Operators: Introduced the null coalescing (??) and spaceship (<=>) operators.
  • Deprecated Features: Many old functions and extensions, like mysql_*, were removed in PHP 7.

3. What are the different types of variables in PHP?

Answer:
PHP has several types of variables:

  • String: Stores a sequence of characters ($name = "John";).
  • Integer: Stores whole numbers ($num = 10;).
  • Float: Stores decimal numbers ($price = 99.99;).
  • Boolean: Stores true or false values.
  • Array: Stores multiple values in one variable ($colors = array("red", "blue", "green");).
  • Object: Stores instances of classes.
  • NULL: Represents a variable with no value ($var = NULL;).

4. How does PHP handle sessions and cookies?

Answer:

  • Sessions: Sessions store user information on the server across multiple pages using session_start() and $_SESSION variables.
  • Cookies: Cookies store user data on the client’s browser using setcookie(). They can persist even after the browser is closed.

Example of a session:

php
session_start();
$_SESSION["username"] = "JohnDoe";

Example of a cookie:

php
setcookie("user", "JohnDoe", time() + (86400 * 30), "/");

5. What is the difference between include, require, include_once, and require_once?

Answer:

  • include: Includes a file and continues execution even if the file is missing.
  • require: Includes a file but stops execution if the file is missing.
  • include_once: Includes a file only once, avoiding duplicate inclusions.
  • require_once: Similar to require, but ensures the file is included only once.

6. What are the different types of errors in PHP?

Answer:

  • Notice: Minor errors that don’t stop script execution (e.g., using an undefined variable).
  • Warning: More serious issues but execution continues (e.g., missing file in include).
  • Parse Error: Syntax errors that prevent script execution.
  • Fatal Error: Critical errors that stop execution (e.g., calling an undefined function).

Example:

php
echo $undefined_var; // Notice error
include("missing_file.php"); // Warning error
echo "Hello World" // Parse error (missing semicolon)

7. How can you prevent SQL injection in PHP?

Answer:
To prevent SQL injection, use prepared statements with PDO or MySQLi.

Example using PDO:

php
$conn = new PDO("mysql:host=localhost;dbname=testdb", "root", "");
$stmt = $conn->prepare("SELECT * FROM users WHERE email = :email");
$stmt->bindParam(':email', $email);
$email = "test@example.com";
$stmt->execute();

8. What is the difference between GET and POST methods?

Answer:

  • GET: Sends data via the URL, visible to users, and has length limitations.
  • POST: Sends data in the request body, hidden from the URL, and more secure for sensitive data.

Example of GET method:

php
<form method="GET" action="process.php">
    <input type="text" name="name">
    <input type="submit">
</form>

Example of POST method:

php
<form method="POST" action="process.php">
    <input type="text" name="name">
    <input type="submit">
</form>

9. What are traits in PHP?

Answer:
Traits allow code reuse in PHP classes without using traditional inheritance.

Example:

php
trait Logger {
    public function log($message) {
        echo "Log message: $message";
    }
}

class User {
    use Logger;
}

$user = new User();
$user->log("User logged in");

10. What is the difference between == and === in PHP?

Answer:

  • == (loose comparison) checks only value equality.
  • === (strict comparison) checks both value and data type.

Example:

php
var_dump(5 == "5"); // true (loose comparison)
var_dump(5 === "5"); // false (strict comparison)

Conclusion

Preparing for a PHP jobs interview requires a strong grasp of fundamental concepts, syntax, and security best practices. Reviewing these questions and practicing with real code examples will help you confidently tackle your next PHP interview. Good luck!

Comments

Post a Comment