Top 15 PHP Interview Questions Asked in 2026 (With Answers)

TL;DR: The top php interview questions 2026 cover PHP fundamentals (arrays, superglobals, OOP), PHP 8 features like enums and readonly properties, MySQL basics, and security topics like SQL injection prevention — asked in roughly that order, fresher to experienced.

You walk into a PHP interview thinking you know the language cold, and then someone asks you the difference between include and require, or worse, "walk me through what happens when PHP 8's match expression falls through with no default." Your mind goes blank for a second. It happens to almost everyone.

Here's the direct answer: interviewers in 2026 are testing three things — do you understand PHP fundamentals, do you know what changed in PHP 8.x, and can you write code that doesn't get exploited in production. This post walks through all 15 questions in the order they usually come up, fresher round first, senior round after.

What is PHP? 

PHP: PHP (Hypertext Preprocessor) is a server-side scripting language built for web development, meaning it runs on the server and generates the HTML your browser receives. Technically, it's an interpreted, loosely-typed language with first-class support for arrays, OOP, and native MySQL integration — think of it as the language that quietly runs a huge chunk of the web behind frameworks like Laravel and WordPress.

According to the PHP official documentation, PHP is a popular general-purpose scripting language especially suited to server-side web development.

Why PHP Interviews Look Different in 2026

Companies aren't just asking "what is a variable in PHP" anymore. PHP 8.x brought enums, readonly properties, and the match expression, and interviewers use these to filter out candidates who learned PHP 5 syntax and never updated.

Laravel questions are also creeping into pure PHP interviews now, since most PHP jobs in 2026 are really Laravel jobs. If you're prepping, don't skip the framework layer entirely — check out our PHP Developer Roadmap 2026 for how core PHP and Laravel fit together in a real job.

Fresher-Level PHP Interview Questions

These are the php interview questions for freshers that show up in almost every first-round screen. Get these solid before you touch anything advanced.

1. What are PHP superglobals?

Superglobals are built-in arrays that are available in every scope of your script — no global keyword needed. $_GET, $_POST, $_SESSION, $_SERVER, and $_COOKIE are the ones you'll actually use.

<?php
// $_POST holds form data submitted via the POST method
$username = $_POST['username'] ?? 'guest'; // null coalescing avoids undefined index warnings

// $_SERVER holds request/environment info
$requestMethod = $_SERVER['REQUEST_METHOD'];

echo "User: $username, Method: $requestMethod";

This grabs a POST value safely and reads the current request method without throwing a warning if the key is missing.

2. Difference between echo and print

echo can take multiple comma-separated arguments and doesn't return a value. print takes exactly one argument and returns 1, which means you can use it inside an expression.

<?php
echo "Hello", " ", "World"; // valid, echo accepts multiple args
$result = print "Logging in..."; // returns 1, so $result is 1

We've got a full breakdown with more edge cases in Difference Between echo and print in PHP. For the exact language-level rules, the PHP manual's echo reference is the source of truth.

3. What's the difference between == and === in PHP?

== compares values after type juggling. === compares value AND type, with no conversion. This is the single most common source of PHP bugs for beginners.

<?php
var_dump(0 == "abc");   // false in PHP 8+ (this changed from PHP 7!)
var_dump("1" == 1);     // true, "1" gets converted to int
var_dump("1" === 1);    // false, string vs int

The 0 == "abc" behavior is a classic gotcha — PHP 7 said true, PHP 8 fixed it to false. If you learned PHP a few years ago, this one bites you in interviews. The full rationale is in the PHP RFC on saner string-to-number comparisons.

4. How do you prevent duplicate values in a PHP array?

<?php
$userIds = [101, 102, 101, 103, 102];
$uniqueIds = array_unique($userIds); // keeps first occurrence, preserves keys

// Re-index if you need clean sequential keys
$uniqueIds = array_values($uniqueIds);

print_r($uniqueIds); // [101, 102, 103]

array_unique() does the filtering, array_values() resets the array keys to 0, 1, 2 so you don't end up with gaps.

5. What is the difference between include and require?

Both pull in code from another file. include throws a warning and keeps executing if the file is missing. require throws a fatal error and stops the script immediately.

6. Sessions vs. Cookies — what's the real difference?

Sessions store data on the server and hand the client a session ID (usually via a cookie). Cookies store data directly in the browser. That means sessions are more secure for sensitive data since the actual data never leaves your server.

<?php
// Session — data lives on the server
session_start();
$_SESSION['user_id'] = 42;

// Cookie — data lives in the browser
setcookie('theme', 'dark', time() + 3600, '/'); // expires in 1 hour

7. What are the four pillars of OOP in PHP?

Encapsulation, Inheritance, Polymorphism, and Abstraction. Encapsulation bundles data and methods together and restricts direct access; inheritance lets a class reuse another class's behavior; polymorphism lets different classes respond to the same method call differently; abstraction hides implementation detail behind a simpler interface.

<?php
abstract class Payment {
    abstract public function process(float $amount): string; // abstraction
}

class CardPayment extends Payment { // inheritance
    private string $cardNumber; // encapsulation

    public function __construct(string $cardNumber) {
        $this->cardNumber = $cardNumber;
    }

    public function process(float $amount): string { // polymorphism
        return "Charged $amount to card ending in " . substr($this->cardNumber, -4);
    }
}

$payment = new CardPayment('4111111111111111');
echo $payment->process(49.99);

This is a common oop php interview questions setup — expect a follow-up asking you to add a PayPalPayment class using the same abstract method.

8. What are magic methods in PHP?

Magic methods start with __ and get called automatically on certain triggers. __construct() runs on object creation, __get()/__set() intercept access to undefined or private properties, and __toString() runs when an object is used as a string.

<?php
class User {
    private array $data = [];

    public function __set(string $name, $value): void {
        $this->data[$name] = $value; // catches writes to undefined properties
    }

    public function __get(string $name) {
        return $this->data[$name] ?? null;
    }
}

$user = new User();
$user->email = 'dev@example.com'; // triggers __set, no explicit property needed
echo $user->email; // triggers __get

9. What's the difference between self:: and static:: in PHP?

self:: refers to the class where the method is written. static:: respects late static binding — it refers to the class that was actually called, which matters in inheritance chains.

<?php
class Base {
    public static function create(): static {
        return new static(); // returns instance of the CALLING class, not Base
    }
}

class Child extends Base {}

$obj = Child::create();
echo get_class($obj); // "Child", not "Base" — this is late static binding

Advanced PHP Interview Questions (10–15)

Once you clear the fresher round, questions shift toward advanced php interview questions — PHP 8 specifics, security, and design patterns. This is where experienced candidates get separated from people who memorized syntax.

10. What's new in PHP 8 that interviewers actually ask about?

Three features come up constantly: enums, readonly properties, and the match expression. All three are php 8 interview questions territory in 2026.

<?php
// Enum — a fixed set of possible values, type-safe
enum OrderStatus: string {
    case Pending = 'pending';
    case Shipped = 'shipped';
    case Delivered = 'delivered';
}

// Readonly property — can only be set once, from inside the class
class Order {
    public function __construct(
        public readonly string $orderId,
        public OrderStatus $status
    ) {}
}

$order = new Order('ORD-1001', OrderStatus::Pending);

// match expression — like switch, but returns a value and uses strict comparison
$message = match ($order->status) {
    OrderStatus::Pending => 'Waiting for shipment',
    OrderStatus::Shipped => 'On its way',
    OrderStatus::Delivered => 'Completed',
};

echo $message; // "Waiting for shipment"

Try $order->orderId = 'ORD-2002'; after construction and PHP throws an error — that's the whole point of readonly. It stops accidental mutation. For the full spec, see the PHP enumerations RFC and the readonly properties RFC.

11. How do you prevent SQL injection in PHP?

This is one of the most-asked php mysql interview questions, and it's also a real production risk. The bug that gets most developers here is string-concatenating user input directly into a query.

Bad code — vulnerable to SQL injection:

<?php
// DANGEROUS: never do this
$username = $_GET['username'];
$query = "SELECT * FROM users WHERE username = '$username'";
$result = mysqli_query($connection, $query);
// An attacker can send username = "' OR '1'='1" and dump the whole table

Good code — using PDO prepared statements:

<?php
$username = $_GET['username'];
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$stmt->execute(['username' => $username]); // value is bound, not concatenated
$user = $stmt->fetch();

Prepared statements separate the SQL structure from the data, so user input can never change the query logic. I've seen this break in production when a "quick fix" query got shipped without a prepared statement because it "was just an internal admin tool" — internal tools get compromised too. Read more in the PHP manual's PDO prepared statements guide and the OWASP SQL Injection reference for real-world attack patterns.

12. Which design patterns are common in PHP applications?

Singleton and Factory come up the most. Singleton ensures only one instance of a class exists (often used for DB connections); Factory centralizes object creation logic.

<?php
class Database {
    private static ?Database $instance = null;
    private function __construct() {} // private constructor blocks `new Database()`

    public static function getInstance(): Database {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }
}

$db1 = Database::getInstance();
$db2 = Database::getInstance();
var_dump($db1 === $db2); // true — same instance, not a new one

This works but has a trade-off: Singletons make unit testing harder because they carry global state. Many modern PHP codebases favor dependency injection instead.

13. How do you optimize PHP application performance?

Interviewers want to hear about opcode caching, database query efficiency, and avoiding N+1 queries — not vague "make it faster" answers.

1. Enable OPcache — caches compiled bytecode so PHP doesn't recompile scripts on every request.
2. Avoid N+1 queries — fetch related data with joins or eager loading instead of looping and querying per row.

   <?php // Bad: N+1 — one query per order inside the loopforeach ($orders as $order) {    $items = $pdo->query("SELECT * FROM items WHERE order_id = {$order['id']}")->fetchAll();}// Good: one query for all items, grouped in PHP$itemsByOrder = [];$stmt = $pdo->query("SELECT * FROM items WHERE order_id IN (" . implode(',', $orderIds) . ")");foreach ($stmt->fetchAll() as $item) {    $itemsByOrder[$item['order_id']][] = $item;}

3. Use array_map/array_filter over manual loops where it improves readability without hurting performance.

14. What is dependency injection in Laravel?

Since laravel interview questions 2026 often get mixed into PHP rounds, know this one. Dependency injection means a class receives its dependencies from outside instead of creating them itself — Laravel's service container handles this automatically.

<?php
class OrderController extends Controller {
    // Laravel's service container automatically injects OrderService here
    public function __construct(private OrderService $orderService) {}

    public function store() {
        return $this->orderService->createOrder();
    }
}

The controller never calls new OrderService() directly, which makes it much easier to swap implementations or mock the service in tests. The official Laravel service container docs go deeper into how this binding and resolution actually works.

15. What is the difference between abstract classes and interfaces in PHP?

An abstract class can have both implemented methods and abstract (unimplemented) ones, and a class can extend only one abstract class. An interface only declares method signatures with no implementation, and a class can implement multiple interfaces.

Common Mistakes and Gotchas in PHP Interviews

This section gets the most search traffic, so let's be specific about where candidates actually lose points.

Mistake 1: Confusing loose and strict comparison in array searches

Bad code:

<?php
$ids = [0, 1, 2, 3];
if (in_array("abc", $ids)) { // loose comparison by default
    echo "Found!"; // this prints in PHP < 8, because "abc" == 0 was true
}

This passes silently in older PHP because of type juggling, and produces confusing bugs in filters and validation logic.

Fixed code:

<?php
$ids = [0, 1, 2, 3];
if (in_array("abc", $ids, true)) { // strict mode, third argument
    echo "Found!";
} else {
    echo "Not found."; // correct output
}

Mistake 2: Not closing database connections or reusing PDO badly

What the docs don't mention clearly enough is that creating a new PDO connection inside a loop is a common performance killer.

<?php
// Bad: new connection every iteration
foreach ($userIds as $id) {
    $pdo = new PDO($dsn, $user, $pass); // expensive, repeated unnecessarily
    $stmt = $pdo->query("SELECT * FROM users WHERE id = $id");
}

// Good: one connection, reused
$pdo = new PDO($dsn, $user, $pass);
foreach ($userIds as $id) {
    $stmt = $pdo->prepare("SELECT * FROM users WHERE id = :id");
    $stmt->execute(['id' => $id]);
}

For more real bugs like this from actual codebases, our 10 Common PHP Bugs in Real-Time Development post covers ten more, and PHP Bugs 21 to 30 continues the series for intermediate-level mistakes. If you're just starting out, Top 10 PHP Bugs Every Beginner Makes is the right place to begin.

Fresher vs. Experienced PHP Interview Focus

If you're figuring out whether PHP is even the right language to specialize in versus Python, we've compared both directly in Python vs PHP: Which Should You Learn First in 2026?

Wrapping Up

These 15 php interview questions 2026 cover what actually gets asked — from echo vs print in the first round to PHP 8's readonly properties and SQL injection prevention in the senior round. The pattern across all of them is the same: interviewers aren't testing memorization, they're testing whether you understand why PHP behaves the way it does.

Your next step: pick three questions from this list you weren't 100% sure about, open a local PHP file, and actually run the code instead of just reading it. That's the difference between recognizing an answer and being able to explain it under pressure.

Keep reading on CodePractice:

• PHP Developer Roadmap 2026: From Core PHP to AI-Powered Backend
• 10 Common PHP Bugs in Real-Time Development (With Fixes)
• The Same Array Bug in PHP, Python & JavaScript — Explained
• Difference Between echo and print in PHP
• How to Prepare for Technical Interviews at Home Without Coaching in 2026

Official references used in this post:

• PHP Official Manual
• PHP 8 Enumerations RFC
• PDO Prepared Statements Documentation
• OWASP SQL Injection Reference
• Laravel Service Container Documentation