Top 10 Essential PHP Interview Questions & Answers

P- PHP learning Tool practice MCQS 

P1. What are the main data types in PHP?

PHP supports scalar types: int, float, string, bool; compound types: array, object; and special types: null, resource. PHP is loosely typed – variables are cast automatically based on context.

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2. What is the difference between include and require?

· include emits a warning and continues execution if the file is not found.

· require throws a fatal error and stops the script.

  Use require for critical dependencies (e.g., configuration), include for optional content.

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3. Explain PHP superglobals. Name a few.

Superglobals are built-in variables

available in all scopes. Key ones:

· $_GET – URL query parameters

· $_POST – form data sent via HTTP POST

· $_SESSION – session data

· $_COOKIE – client-side cookies

· $_SERVER – server and execution environment info

· $_FILES – uploaded files

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4. How do you connect to a MySQL database securely?

Use PDO or MySQLi with prepared statements to prevent SQL injection. Example with PDO:

```php

$pdo = new PDO('mysql:host=localhost;dbname=test', $user, $pass);

$stmt = $pdo->prepare('SELECT * FROM users WHERE email = ?');

$stmt->execute([$email]);

$user = $stmt->fetch();

```

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

· == (loose equality) compares values after type juggling (e.g., 1 == '1' is true).

· === (strict equality) checks both value and type – 1 === '1' is false.

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6. Explain basic OOP concepts in PHP: class, inheritance, polymorphism.

· Class – blueprint for objects.

· Inheritance – a child class extends a parent using extends, gaining all

non‑private properties/methods.

· Polymorphism – methods with the same name can behave differently across classes (achieved via interfaces or abstract classes).

  Example:

```php

abstract class Animal {

    abstract public function makeSound();

}

class Dog extends Animal {

    public function makeSound() { echo "Bark"; }

}

```

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7. How do you handle exceptions in PHP?

Use try, catch, and optionally finally:

```php

try {

    // code that may throw an exception

} catch (Exception $e) {

    echo 'Caught: ' . $e->getMessage();

} finally {

    // always executed

}

```

You can also create custom exception classes by extending Exception.

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8. Sessions vs. Cookies – what’s the difference?

· Sessions store data on the server; a session ID is stored in a cookie (or URL). Data is temporary and cleared when the session ends.

· Cookies store data on the client side (browser) and have expiration dates. They are limited to ~4KB and are less secure.

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9. How can you prevent XSS (Cross‑Site Scripting) attacks?

Always escape output. U

se htmlspecialchars($string, ENT_QUOTES, 'UTF-8') when rendering user‑supplied data in HTML. For input, validate and sanitize, but never trust user input.

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10. What are PHP magic methods? Give two examples.

Magic methods start with __ and are called automatically.

· __construct() – invoked when an object is instantiated.

· __toString() – defines how an object behaves when treated as a string.

  Others: __get(), __set(), __call(), __destruct(), etc.

--- PHP learning Tool practice MCQS 

These questions cover the fundamentals, security, and modern practices – a solid foundation for any PHP developer. Good luck!