Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 166-180.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 166-180.


24 min read

Explore GitFlow and Trunk-based flow, and grasp the concept of memoization. Understand the placement of business logic within the MVC Design Pattern and learn SQL tricks like updating values without temporary tables.

Dive into coding challenges, from creating a stream sampler to traversing complex tree structures. Explore DTO and Value Objects and their application scenarios.

Differentiate between linked lists and arrays, and delve into sorting algorithms.

Create a JWT authentication middleware in Laravel, grasp the essence of AJAX requests, and discover strategies to process incoming requests efficiently.

166. Do you have any tips on how to optimize PHP code for performance?

Formal Explanation: Optimizing PHP code for performance involves various techniques and practices that aim to make the code execute faster and consume fewer resources. These optimizations can lead to improved response times, reduced server load, and a better user experience.

Simplified Explanation with Examples:

To make your PHP code run faster and use less memory, consider these tips:

  1. Use Proper Data Structures: Choose the appropriate data structures (arrays, lists, maps) for efficient data manipulation.

  2. Minimize Database Queries: Reduce unnecessary database queries by using caching and batching operations.

  3. Use Opcode Caching: Implement opcode caching with tools like OPcache to avoid repetitive compilation of scripts.

  4. Avoid Global Variables: Minimize the use of global variables to prevent unnecessary memory consumption.

  5. Optimize Loops: Optimize loops by reducing iterations and avoiding complex operations within loops.

  6. Use Function Calls Wisely: Avoid excessive function calls, especially within loops, to reduce overhead.

  7. Lazy Loading: Load resources only when needed to avoid unnecessary loading during application startup.

  8. Avoid Excessive String Manipulation: String concatenation can be resource-intensive; use array joins or sprintf instead.

  9. Use Efficient Algorithms: Choose algorithms with better time complexity for sorting and searching operations.

  10. Reduce I/O Operations: Minimize file I/O and database queries to avoid waiting for external resources.

Detailed Explanation with Examples:

Optimizing PHP code for performance is crucial for ensuring fast response times and efficient resource utilization. Here are more than 10 examples of optimization techniques:

  1. Use Proper Data Structures: Instead of linear search in an array, use associative arrays or maps for faster lookups.

  2. Minimize Database Queries: Implement query caching or use ORM tools to batch database queries, reducing the number of round-trips.

  3. Use Opcode Caching: Install and configure OPcache to store compiled PHP scripts in memory, reducing script compilation overhead.

  4. Avoid Global Variables: Pass variables as function parameters or use dependency injection to reduce memory usage and improve code readability.

  5. Optimize Loops: Avoid nested loops when possible, and use algorithms like binary search for large datasets.

  6. Use Function Calls Wisely: Minimize the use of unnecessary function calls within loops, as they can impact performance.

  7. Lazy Loading: Load resources (like images or libraries) only when they are actually needed to speed up application startup.

  8. Avoid Excessive String Manipulation: Instead of concatenating strings in a loop, use array joins or sprintf for better performance.

  9. Use Efficient Algorithms: Choose algorithms with lower time complexity, like quicksort or mergesort, for better performance in sorting.

  10. Reduce I/O Operations: Cache file reads or database results, and use efficient database indexing to reduce I/O wait times.

  11. Minimize Network Calls: Use asynchronous operations for network requests to prevent the application from waiting for responses.

  12. Optimize Regular Expressions: Use more efficient regular expressions or string functions for pattern matching to avoid performance bottlenecks.

  13. Use Output Buffering: Implement output buffering to send response content in chunks instead of all at once, improving perceived speed.

  14. Use GZIP Compression: Enable GZIP compression for responses to reduce data transfer sizes and improve page load times.

  15. Profile and Benchmark: Regularly profile and benchmark your code to identify performance bottlenecks and track improvements.

By implementing these optimization techniques, you can significantly enhance the performance of your PHP applications, leading to faster response times, better scalability, and a smoother user experience.

167. What is GitFlow? How does it differ from Trunk-based flow? When should each be used?

Formal Explanation: GitFlow and Trunk-based flow are two branching strategies used in version control with Git. GitFlow follows a structured branching model with multiple long-lived branches, while Trunk-based flow promotes shorter-lived branches and frequent integration into the main branch. GitFlow is suitable for larger projects with complex release management, while Trunk-based flow is best for smaller, agile teams aiming for continuous integration and faster releases.

Simplified Explanation with Example:

GitFlow is a branching model with separate branches for features, releases, and hotfixes. Trunk-based flow involves frequent integration into the main branch. Use GitFlow for bigger projects with defined release cycles and Trunk-based flow for smaller projects with rapid releases.

Detailed Explanation with Examples:


In GitFlow, there are several long-lived branches:

  • Master: Represents the main codebase and is used for production releases.

  • Develop: Integrates feature branches and prepares them for release.

  • Feature: Short-lived branches for developing new features.

  • Release: Prepares code for production release.

  • Hotfix: Fixes critical issues in the master branch.

# Create a new feature branch
git checkout -b feature/new-feature develop

# Develop the feature
# Merge the feature back to the develop branch
git checkout develop
git merge --no-ff feature/new-feature
git branch -d feature/new-feature

# Prepare a release branch
git checkout -b release/1.0.0 develop

# Finish the release and merge it to both master and develop branches
git checkout master
git merge --no-ff release/1.0.0
git checkout develop
git merge --no-ff release/1.0.0
git branch -d release/1.0.0

# Create a hotfix branch to fix critical issues
git checkout -b hotfix/bug-fix master

# Merge the hotfix to master and develop
git checkout master
git merge --no-ff hotfix/bug-fix
git checkout develop
git merge --no-ff hotfix/bug-fix
git branch -d hotfix/bug-fix

Trunk-based Flow:

Trunk-based flow involves short-lived feature branches that are frequently merged into the main branch. This approach requires continuous integration and automated testing.

# Create a feature branch
git checkout -b feature/new-feature

# Develop the feature
# Frequently merge changes from the main branch
git checkout main
git merge feature/new-feature

# Continue development and integration
git checkout feature/new-feature
# Frequent merges and testing

# Merge the feature to the main branch
git checkout main
git merge feature/new-feature

When to Use:

  • GitFlow: Suitable for larger projects with complex release cycles, multiple features, and clear separation between development and release phases.

  • Trunk-based Flow: Best for smaller teams, startups, or projects that require rapid releases, continuous integration, and minimal branching overhead.

Choosing between GitFlow and Trunk-based flow depends on project size, team structure, release frequency, and development practices.

168. What is memoization

Formal Explanation: Memoization is an optimization technique used to store the results of expensive function calls and return the cached result when the same inputs occur again. This helps to avoid redundant computations and improve performance. An alternative to memoization is using dynamic programming techniques to solve similar problems, which can lead to improved time complexity.

Simplified Explanation with Example:

Memoization stores the results of expensive calculations to avoid repeating them. An alternative is solving problems using dynamic programming techniques. For example, caching Fibonacci numbers to speed up calculations is memoization.

Detailed Explanation with Example:


Suppose you have a function to calculate Fibonacci numbers:

function fib($n, &$memo = []) {
    if (isset($memo[$n])) {
        return $memo[$n];
    if ($n <= 2) {
        return 1;
    $memo[$n] = fib($n - 1, $memo) + fib($n - 2, $memo);
    return $memo[$n];

echo fib(6);  // Output: 8

In this example, the fib function uses an associative array ($memo) to store previously computed Fibonacci numbers. Before calculating a Fibonacci number, it checks if the result is already in the $memo array and returns it if available. This significantly reduces the number of redundant calculations.

Alternative: Dynamic Programming:

Dynamic programming involves breaking down a problem into smaller subproblems and solving each subproblem only once, storing their solutions for future reference. For example, solving the Fibonacci sequence using bottom-up dynamic programming:

function fib($n) {
    if ($n <= 2) {
        return 1;
    $dp = array_fill(0, $n + 1, 0);
    $dp[1] = $dp[2] = 1;
    for ($i = 3; $i <= $n; $i++) {
        $dp[$i] = $dp[$i - 1] + $dp[$i - 2];
    return $dp[$n];

echo fib(6);  // Output: 8

In this approach, the Fibonacci numbers are computed iteratively using an array ($dp) to store solutions of subproblems. This eliminates redundant calculations and improves efficiency.

Memoization vs. Dynamic Programming:

Memoization is suitable for recursive algorithms where subproblems are solved repeatedly with the same inputs. Dynamic programming is used when a problem can be broken down into overlapping subproblems and can be solved iteratively using previously computed results.

Both techniques optimize computations and enhance performance, but the choice depends on the nature of the problem and the optimal approach for solving it efficiently.

169. Where do we put the business logic in the MVC Design Pattern?

Formal Explanation: In the MVC (Model-View-Controller) design pattern, the business logic is primarily placed in the Model component. The Model represents the application's data and rules, including the business logic that operates on the data. This separation allows for a clear distinction between the presentation layer (View) and the data manipulation and processing layer (Model).

Simplified Explanation with Example: In MVC, the business logic goes into the Model. This is where data manipulation and rules are defined. For instance, validating user inputs, performing calculations, and interacting with the database happen in the Model.

The role of a controller is to manage the application's logic. It handles the specific interactions between your application and the "domain of knowledge" it's connected to. In other words, the controller is responsible for orchestrating how your application interacts with its unique area of expertise.

On the other hand, the model focuses on logic that stands independent of the application itself. This type of logic should remain valid regardless of the specific application it's used in. It's designed to hold true in all conceivable scenarios within the "domain of knowledge" it's associated with.

Detailed Explanation with Example:

Let's consider a simple example of a user registration system using MVC:

  1. Model: The Model contains the business logic. It handles interactions with the database, data validation, and processing. For example:

     class UserModel {
         public function registerUser($userData) {
             // Validate user data
             if ($this->validateUserData($userData)) {
                 // Save user data to the database
                 $userId = $this->saveUserData($userData);
                 return $userId;
             return false;
         private function validateUserData($data) {
             // Perform validation checks
             // Return true if valid, false otherwise
         private function saveUserData($data) {
             // Save user data to the database
             // Return the user's ID
  2. View: The View is responsible for presenting the data to the user. It displays the information but doesn't contain the business logic. For instance, rendering HTML templates to show the registration form or success message.

     class UserView {
         public function showRegistrationForm() {
             // Display the registration form
         public function showSuccessMessage($userId) {
             // Display a success message with the user's ID
  3. Controller: The Controller acts as an intermediary between the Model and View. It receives user inputs, interacts with the Model to perform actions, and then updates the View to reflect the changes.

     class UserController {
         public function register() {
             // User submits registration form
             $userData = // Extract user data from form
             $userModel = new UserModel();
             $userId = $userModel->registerUser($userData);
             if ($userId) {
                 $userView = new UserView();
             } else {
                 // Display error message

In this example, the business logic of validating user data, saving it to the database, and managing the registration process resides in the Model component. The View component handles the presentation, while the Controller coordinates interactions between the Model and View based on user actions.

Placing business logic in the Model promotes separation of concerns and maintainability in the application.

170. You have a table with customers, with gender 'm' and 'f'. Write a query to update 'm' with 'f' and 'f' with 'm' in a single query, without using temporary tables.

To update the gender values 'm' to 'f' and 'f' to 'm' in a single query without using temporary tables, you can use a combination of a CASE statement and an UPDATE statement. This approach allows you to perform the updates using conditional logic within a single query.

Detailed Explanation with Example: Let's say you have the following 'customers' table:


You want to update 'm' to 'f' and 'f' to 'm'. The query provided earlier will perform this update in a single query:

UPDATE customers
SET gender = CASE
    WHEN gender = 'm' THEN 'f'
    WHEN gender = 'f' THEN 'm'
    ELSE gender

After executing this query, the 'customers' table will be updated as follows:


The CASE statement within the UPDATE query allows you to conditionally update the 'gender' column values based on the current values. This approach eliminates the need for temporary tables and performs the update in a single query.

171. Write a program called "stream-sampler" that receives and processes an input stream consisting of single characters.

Formal Explanation: To create a program that samples characters from an input stream, you can use a reservoir sampling algorithm. Reservoir sampling allows you to select a random sample of a specified size from a stream of data without knowing the total size of the stream in advance.

Simplified Explanation with Example: The program "stream-sampler" reads characters from an input stream and samples a subset of characters using reservoir sampling. It maintains a reservoir (sample) of a fixed size. As characters are read from the input stream, they are added to the reservoir with decreasing probability. The reservoir is updated to maintain the desired sample size. This approach ensures that each character has an equal chance of being selected for the sample.

Detailed Explanation with Example in PHP: Here's an example implementation of the "stream-sampler" program in PHP:

class StreamSampler {
    private $reservoir = [];
    private $sampleSize;
    private $totalRead = 0;

    public function __construct($sampleSize) {
        $this->sampleSize = $sampleSize;

    public function processStream($stream) {
        while (($char = fgetc($stream)) !== false) {

            if (count($this->reservoir) < $this->sampleSize) {
                $this->reservoir[] = $char;
            } else {
                $randomIndex = rand(0, $this->totalRead - 1);
                if ($randomIndex < $this->sampleSize) {
                    $this->reservoir[$randomIndex] = $char;

    public function getSample() {
        return $this->reservoir;

// Usage example
$sampleSize = 5;
$stream = fopen('input.txt', 'r'); // Replace with your input stream
$streamSampler = new StreamSampler($sampleSize);
$sample = $streamSampler->getSample();

echo "Sampled characters: " . implode(', ', $sample) . "\n";

In this example, the StreamSampler class implements the reservoir sampling algorithm. The processStream method reads characters from the input stream and updates the reservoir based on the algorithm. The getSample method returns the sampled characters.

Keep in mind that the quality of the sample may vary based on the length of the input stream and the sample size. Reservoir sampling provides a simple and memory-efficient way to sample data from a stream without knowing the stream's size in advance.

172. How can you retrieve data from more than three tables without using the JOIN clause?

Formal Explanation: To retrieve data from multiple tables without using the JOIN clause, you can use subqueries or nested queries. Subqueries involve querying one table within the context of another query. This allows you to fetch data from multiple tables without explicitly using the JOIN clause.

Simplified Explanation with Example: You can use subqueries to retrieve data from multiple tables without using the JOIN clause. Subqueries involve running queries inside other queries. This approach can be useful when you want to combine data from different tables based on certain conditions.

Detailed Explanation with Example in SQL: Here's an example of how you can retrieve data from more than three tables using subqueries:

Suppose you have three tables: customers, orders, and order_items. You want to retrieve the names of customers along with their total order amounts, without using the JOIN clause.

SELECT AS customer_name,
    (SELECT SUM(o.amount) FROM orders o WHERE o.customer_id = AS total_order_amount
FROM customers c;

In this example, the subquery (SELECT SUM(o.amount) FROM orders o WHERE o.customer_id = calculates the total order amount for each customer. The main query retrieves the customer names and the corresponding total order amounts using the subquery.

While subqueries can be used to retrieve data from multiple tables without using JOIN, it's important to note that subqueries can be less efficient compared to using proper JOIN clauses, especially for larger datasets. Additionally, subqueries may result in more complex and less readable queries. Use subqueries when necessary, but consider optimizing your query structure for performance and readability.

173. How can you traverse a tree data structure?

Formal Explanation: Tree traversal involves systematically visiting all the nodes in a tree data structure. There are different methods for traversing trees, including in-order, pre-order, post-order, and level-order traversal. Each traversal method defines a specific order in which the nodes are visited.

Simplified Explanation with Example: Traversing a tree means visiting each node in a specific order. Imagine a family tree, where you start from a person and explore their ancestors and descendants following a specific pattern.

Detailed Explanation with Example in PHP:

Let's consider a binary tree structure and explore different traversal methods using PHP code:

class TreeNode {
    public $value;
    public $left;
    public $right;

    public function __construct($value) {
        $this->value = $value;
        $this->left = null;
        $this->right = null;

function inOrderTraversal($node) {
    if ($node !== null) {
        echo $node->value . " ";

function preOrderTraversal($node) {
    if ($node !== null) {
        echo $node->value . " ";

function postOrderTraversal($node) {
    if ($node !== null) {
        echo $node->value . " ";

// Construct a simple binary tree
$root = new TreeNode(1);
$root->left = new TreeNode(2);
$root->right = new TreeNode(3);
$root->left->left = new TreeNode(4);
$root->left->right = new TreeNode(5);

echo "In-order traversal: ";
echo "\n";

echo "Pre-order traversal: ";
echo "\n";

echo "Post-order traversal: ";
echo "\n";

In the above example, we have a simple binary tree, and we've defined functions for in-order, pre-order, and post-order traversals. The tree is traversed following the specified order, and the values of nodes are printed. The order in which nodes are visited depends on the traversal method.

Tree traversal is an essential concept in computer science and is widely used for operations like searching, printing, and modifying tree structures. Different traversal methods serve various purposes and are used based on the requirements of the application.

174. What are DTO and Value Object? When should they be used and in what scenarios?

Formal Explanation: DTO (Data Transfer Object) and Value Object are two design patterns used in software development. DTO is used to transfer data between layers or components, while Value Object is used to represent immutable values with distinct identities.

Simplified Explanation with Example: DTO is like a courier that transports data between different parts of an application, ensuring the correct format and structure. Value Object is like a sealed envelope that holds a specific value and cannot be changed once created.

Detailed Explanation with Examples:

DTO (Data Transfer Object):

  • A DTO is an object used to transfer data between different parts of an application, such as between the client and the server or between different layers.

  • It is often used to encapsulate and structure data in a way that fits the needs of the receiving component.

  • DTOs are helpful when you want to limit the amount of data transferred over a network, prevent exposing sensitive information, or provide a simplified view of complex data.

  • For example, in a web application, when a client sends data to the server to create a new user account, the data can be packaged into a UserDTO object that includes only the necessary fields like username and email.

Example in PHP 8:

class UserDTO {
    public function __construct(private string $username, private string $email) {}

    public function getUsername(): string {
        return $this->username;

    public function getEmail(): string {
        return $this->email;

// Usage
$userDto = new UserDTO('john_doe', '');

Value Object:

  • A Value Object is an object that represents a value with distinct attributes and characteristics. It is immutable, meaning its values cannot be changed after creation.

  • Value Objects are used to represent concepts that have significance beyond their attributes. They are identified by their values rather than their identity.

  • Value Objects are useful for ensuring data integrity and avoiding ambiguity. For example, a Money value object could encapsulate the amount and currency of a monetary value, preventing arithmetic mistakes and ensuring consistency.

  • Value Objects are typically used within domain-driven design to model concepts like dates, times, geographic coordinates, and more.

Example in PHP 8:

class Money {
    public function __construct(private int $amount, private string $currency) {}

    public function getAmount(): int {
        return $this->amount;

    public function getCurrency(): string {
        return $this->currency;

// Usage
$price = new Money(1999, 'USD');

In summary, DTOs are used to transfer data between components, while Value Objects represent immutable values with distinct attributes and are used to ensure data integrity and consistency in domain models. The choice to use DTOs and Value Objects depends on the specific requirements and design of the application.

176. What is the difference between a linked list and an array?

Formal Explanation: A linked list and an array are both data structures used to store collections of elements, but they have different characteristics in terms of memory usage, access time, and operations.

Simplified Explanation with Example: A linked list is a linear data structure where each element (node) contains a value and a reference to the next element. An array is a data structure where elements are stored in contiguous memory locations and can be accessed using an index.

Detailed Explanation with Example: Linked List:

  • A linked list is a collection of nodes where each node contains two parts: the value and a reference to the next node.

  • Inserting or deleting elements in a linked list is efficient as it involves changing the references.

  • Linked lists are dynamic in size and can be easily resized.

  • Accessing elements requires traversing the list from the beginning, which makes it less efficient for random access.

  • Linked lists are often used when dynamic insertions and deletions are frequent.

class Node {
    public $value;
    public $next;

    public function __construct($value) {
        $this->value = $value;
        $this->next = null;

$node1 = new Node("Alice");
$node2 = new Node("Bob");
$node3 = new Node("Charlie");

$node1->next = $node2;
$node2->next = $node3;


  • An array is a collection of elements stored in contiguous memory locations.

  • Elements in an array can be accessed directly using their index, which makes random access efficient.

  • Inserting or deleting elements in an array can be less efficient, especially if done in the middle, as it may require shifting elements.

  • Arrays have a fixed size and may need to be resized with reallocation and copying.

  • Arrays are often used when random access and a fixed size are required.

$array = ["Alice", "Bob", "Charlie"];

In this example, accessing elements using indexes is more efficient in an array, whereas linked lists are better for frequent insertions and deletions.

In summary, linked lists and arrays have their own strengths and weaknesses, and the choice between them depends on the specific use case and performance requirements.

177. Write a function to sort an array quickly without using PHP built-in sorting functions. Also, provide a few sorting algorithms based on this function.

Formal Explanation: A sorting algorithm is a method used to arrange elements of an array or list in a specific order. There are various sorting algorithms available, each with its own time complexity and performance characteristics.

Detailed Explanation with PHP Example (Using Bubble Sort and Quick Sort): Here, we'll implement two sorting algorithms: Bubble Sort and Quick Sort.

  1. Bubble Sort:
  • Bubble Sort repeatedly steps through the list, compares adjacent elements, and swaps them if they're in the wrong order.
function bubbleSort($arr) {
    $n = count($arr);
    for ($i = 0; $i < $n - 1; $i++) {
        for ($j = 0; $j < $n - $i - 1; $j++) {
            if ($arr[$j] > $arr[$j + 1]) {
                $temp = $arr[$j];
                $arr[$j] = $arr[$j + 1];
                $arr[$j + 1] = $temp;
    return $arr;
  1. Quick Sort:
  • Quick Sort is a divide-and-conquer algorithm that selects a "pivot" element and partitions the array into two sub-arrays.
function quickSort($arr) {
    $n = count($arr);
    if ($n <= 1) {
        return $arr;
    $pivot = $arr[0];
    $left = $right = [];
    for ($i = 1; $i < $n; $i++) {
        if ($arr[$i] < $pivot) {
            $left[] = $arr[$i];
        } else {
            $right[] = $arr[$i];
    return array_merge(quickSort($left), [$pivot], quickSort($right));

Using the provided bubbleSort and quickSort functions, you can sort an array quickly without using PHP built-in sorting functions.

It's worth noting that while these sorting algorithms are useful for educational purposes, PHP's built-in sorting functions like sort, asort, and usort are highly optimized and generally preferred for practical use due to their efficiency and performance.

178. Create a middleware to authenticate against JSON Web Tokens (JWT) in Laravel.

Formal Explanation: Middleware in Laravel is a way to filter HTTP requests entering your application. Authentication middleware can be used to verify the validity of a JWT before allowing access to certain routes or endpoints.

Simplified Explanation with Example: Middleware is like a security guard that checks if you have the right access before entering a certain area. For JWT authentication, the middleware checks if the provided token is valid before letting you access protected routes.

Detailed Explanation with Laravel Example:

  1. Create Middleware: Create a new middleware named JwtAuthMiddleware using the following command:
php artisan make:middleware JwtAuthMiddleware
  1. Edit the Middleware: Open the generated JwtAuthMiddleware file (app/Http/Middleware/JwtAuthMiddleware.php) and modify the handle method to implement JWT authentication logic.
use Closure;
use Illuminate\Http\Request;
use JWTAuth; // Make sure to import the JWTAuth class

class JwtAuthMiddleware
    public function handle(Request $request, Closure $next)
        try {
            $user = JWTAuth::parseToken()->authenticate();
        } catch (\Exception $e) {
            return response()->json(['error' => 'Unauthorized'], 401);

        // Store the authenticated user for further use
        $request->auth = $user;

        return $next($request);
  1. Register Middleware: Add the JwtAuthMiddleware to the $routeMiddleware array in the app/Http/Kernel.php file.
protected $routeMiddleware = [
    // ...
    'jwt.auth' => \App\Http\Middleware\JwtAuthMiddleware::class,
  1. Use the Middleware: You can now use the jwt.auth middleware in your routes to protect them with JWT authentication.
Route::middleware(['jwt.auth'])->group(function () {
    Route::get('/protected', 'ProtectedController@index');

Now, the JwtAuthMiddleware middleware will check the validity of the JWT token before granting access to the /protected route.

Keep in mind that this is a basic example of implementing JWT authentication middleware in Laravel. In a real-world scenario, you may want to customize the error responses and handle token expiration, refresh, and other aspects of JWT authentication more comprehensively.

179. What is an AJAX request?

Formal Explanation: An AJAX (Asynchronous JavaScript and XML) request is a technique in web development that allows you to send and receive data from a web server without having to reload the entire web page. It enables you to update parts of a web page asynchronously, providing a more seamless user experience.

Simplified Explanation with Example: Think of AJAX as a way to fetch or send data from/to a server without making the user wait for the entire page to reload. It's like ordering food online and getting updates on the delivery status without refreshing the entire menu page.

Detailed Explanation with Example in JavaScript: In JavaScript, you can use the XMLHttpRequest object or the modern Fetch API to make AJAX requests.

  1. Using XMLHttpRequest (Older method):
// Create a new XMLHttpRequest object
var xhr = new XMLHttpRequest();

// Configure the request'GET', '', true);

// Set up a callback for when the request completes
xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
        var responseData = JSON.parse(xhr.responseText);
        // Process the responseData

// Send the request
  1. Using Fetch API (Modern method):
// Make an AJAX request using the Fetch API
    .then(response => response.json())
    .then(data => {
        // Process the data
    .catch(error => {
        console.error('Error fetching data:', error);

In both examples, an AJAX request is made to the server to fetch data from the URL ( Once the data is received, it can be processed and updated on the webpage without requiring a full page reload.

Remember that AJAX requests can be used for various purposes, such as retrieving data, sending form data, or interacting with APIs, all while providing a smoother and more dynamic user experience.

180. How can you quickly process incoming requests without keeping the connection open when the logic takes a long time to execute?

Formal Explanation: To quickly process incoming requests without blocking the connection, you can use asynchronous programming or multithreading. In an asynchronous model, you can use mechanisms such as promises or asynchronous functions to perform long-running operations in parallel without blocking the main thread. In a multithreaded approach, using threads or processes, you can divide the long operation into separate parallel tasks.

Simplified Explanation with Example: Imagine you have an application that handles requests for image processing. Instead of waiting for the image to be fully processed, you can asynchronously pass the processing operation to another module and continue handling other requests.

Detailed Explanation with Example in PHP: Suppose you have a PHP web application that processes requests to generate reports. Report generation can take some time. Instead of keeping the connection open and waiting for completion, you can asynchronously handle the request.

Example using the ReactPHP library for asynchronous programming in PHP:

use React\EventLoop\Factory;
use React\Http\Server;
use React\Http\Response;

require 'vendor/autoload.php';

$loop = Factory::create();

$server = new Server(function ($request) use ($loop) {
    // Asynchronous operation, such as report generation
    $asyncOperation = function () use ($loop) {
        return new React\Promise\Promise(function ($resolve) use ($loop) {
            $loop->addTimer(2, function () use ($resolve) {
                $report = 'Report is ready';

    return $asyncOperation()->then(function ($report) {
        return new Response(
            array('Content-Type' => 'text/plain'),

$socket = new React\Socket\Server('', $loop);


In this example, the server is configured to asynchronously handle requests. Upon receiving a request, it initiates an asynchronous operation (report generation) and returns an HTTP response with the message "Report is ready" after two seconds.

Asynchronous programming efficiently utilizes server resources and avoids blocking connections, even during long-running operations.

Regarding closing connections, in PHP, the connections are typically managed by the web server (e.g., Apache or Nginx) and PHP itself. When using asynchronous frameworks like ReactPHP, the server-side code generally doesn't handle connection closure explicitly, as it's managed by the server library. The server library handles the low-level networking and connection management, ensuring that connections are properly opened and closed as needed.

Previous articles of the series:

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 1-15.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 16-30.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 31-45.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 46-60.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 61-75.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 91-105.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 106-120.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 121-135.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 136-150.

Mastering the PHP Developer Interview: 100+ Technical Questions Answered. 151-165.