PHP Introduction

PHP stands for Hypertext Preprocessor. It is an open-source, widely used language for web development. Developers can create dynamic and interactive websites by embedding PHP code into HTML. PHP can handle data processing, session management, form handling, and database integration. The latest version of PHP is PHP 8.4, released in 2024.

• PHP is a server-side scripting language that generates dynamic content on the server and interacts with databases, forms, and sessions.
• PHP supports easy interaction with databases like MySQL, enabling efficient data handling.
• PHP runs on multiple operating systems and works with popular web servers like Apache and Nginx.

Syntax:

<?php 
    // PHP code goes here 
?>

"Hello, World!" Program

A "Hello, World!" program is the simplest way to get started with any programming language. Here’s how you can write one using PHP.

<?php
  echo "Hello, World!";
?>

Hello, World!

In this example

• <?php and ?> are the PHP tags that embed PHP code into an HTML document.
• echo is a PHP function used to output text to the browser.
• "Hello, World!" is the text that will be displayed when the PHP code is executed.

How PHP Works?

Below are the following steps, which show how PHP works:

Step 1: User Requests the Page

• The user enters a URL into a web browser or clicks on a link, making an HTTP request to the web server.

Step 2: Web Server Receives the Request

• The web server (Apache, Nginx, etc.) receives the HTTP request. The request is directed to PHP for processing.
• The PHP script located on the server is executed.

Step 3: PHP Processes the Request

• The PHP script processes any server-side logic, such as handling form submissions, processing data, or making requests to a database.
• If the PHP script requires database interaction, an SQL query is sent to the database.

Step 4: Database Interaction

• The PHP script sends a request to the database (e.g., MySQL) with an SQL query.
• The database processes the query and sends a response (results of the query) back to the PHP script.

Step 5: PHP Responds with Dynamic Content

• Based on the database response, the PHP script processes and prepares the output (dynamic HTML or other content) that will be sent back to the user's browser.
• This response is returned as an HTTP response to the web browser.

Step 6: Web Browser Receives the Response

• The web browser receives the HTTP response, which includes dynamic content generated by PHP.
• The browser renders the content on the user's screen.

This is how the PHP workflow operates in web applications, where PHP interacts with a database and a web server to generate dynamic content for the user.

What is a PHP File?

A PHP file is:

• A file containing PHP code, used to create dynamic web pages.
• It contains HTML, CSS, JavaScript, and PHP code together.
• Runs on a web server with PHP installed (e.g., Apache, Nginx), and the output is sent to the browser as plain HTML.
• It is saved with a .php extension.

What Can PHP Do?

• Generate Dynamic Content: PHP creates dynamic web pages based on user input.
• Manage Files: PHP can create, open, read, write, and delete files on the server.
• Process Form Data: PHP collects and processes data from web forms.
• Handle Cookies: PHP can send and receive cookies to manage sessions.
• Interact with Databases: PHP adds, deletes, and modifies data in databases.
• Control User Access: PHP can manage login systems and user permissions.
• Encrypt Data: PHP can encrypt sensitive information for security.

Why is PHP still popular?

• Widely Used: PHP runs on more than 77% of websites, including popular sites like WordPress and Facebook.
• Cross-Platform: Works on Windows, Linux, and macOS.
• WordPress Backend: PHP is the foundation of WordPress, used by 75% of CMS-based websites.
• Integrates Easily: Works well with HTML and JavaScript to build dynamic websites.
• Fast Performance: PHP 8 introduced Just-In-Time (JIT) compilation for faster execution.

PHP is a Loosely Typed Language

PHP is considered a loosely typed language, meaning you do not need to specify the data type when declaring a variable. PHP will automatically interpret the variable’s type based on the value assigned to it at runtime.

• In PHP 7, type declarations were introduced.
• This allows developers to define the expected data type for function parameters.
• By enabling strict typing, PHP will raise a "Fatal Error" if the passed argument does not match the declared type.
• PHP dynamically assigns a data type to a variable based on the value it holds. Since the language is not strongly typed, operations like adding a string to an integer can be performed without causing an error.

Now, let us understand with the help of the example:

Without Using Strict Mode

In this example, the strict mode is not enabled, so it will change the string "3" to int 3 and it will return result 8.

<?php
function addNumbers(int $a, int $b) {
    return $a + $b;
}
echo addNumbers(5, "3"); 
?>

8

Using Strict Mode

In this, the strict mode is enabled, so "3" is not an integer it is a string, so the error will be thrown.

<?php
    declare(strict_types=1); // Strict mode enabled

function addNumbers(int $a, int $b) {
    return $a + $b;
}

echo addNumbers(5, "3"); // Throws Fatal Error: Uncaught TypeError: Argument 2 passed to addNumbers
?>

Fatal error: Uncaught TypeError: Argument 2 passed to addNumbers() must be of the type int, string given, called in /home/guest/sandbox/Solution.php on line 8 and defined in /home/guest/sandbox/Solut...

Key Features of PHP

• Client-Side Scripting: PHP can generate dynamic HTML that is sent to the browser. While it runs on the server, the content it generates can be displayed in the client’s browser.
• Database Handling: PHP easily connects to databases like MySQL, PostgreSQL, and SQLite, allowing for efficient data management and storage in web applications.
• Simple Learning Curve: PHP’s syntax is easy to learn, especially for those with basic knowledge of HTML and programming concepts.
• Rich Ecosystem: PHP offers many libraries and frameworks like Laravel and Symfony, which make development faster and more efficient.
• Scalability: PHP is highly scalable, allowing developers to create websites that can grow in terms of traffic and functionality.
• Asynchronous Support: PHP, through the use of libraries and frameworks like ReactPHP, supports asynchronous programming, allowing developers to handle multiple requests concurrently.

Applications of PHP

• Web Development: PHP is widely used for creating dynamic websites and web applications by generating interactive content, handling user inputs, and interacting with databases.
• Command-Line Scripting: PHP can be used to write command-line scripts for automating repetitive tasks, such as data processing or system monitoring.
• Game Development: PHP is used for backend logic in browser-based multiplayer games, handling user authentication, scores, and game state.
• Real-Time Applications: PHP supports real-time applications like chat systems and live updates, typically using AJAX or WebSockets.
• File Management: PHP handles file uploads and creates file management systems for organizing and downloading files.

Limitations of PHP

• Security Risks: If not used properly, PHP can be vulnerable to attacks like SQL injection, XSS, and CSRF. Developers must follow security best practices.
• Not Ideal for Command-Line: While PHP can be run from the command line, it’s mainly designed for web development, so its performance for general-purpose tasks may not be as efficient as other languages.
• Limited Support for Multi-threading: While PHP can handle concurrent requests by asynchronous frameworks, multi-threaded support is limited compared to languages like Java or Node.js.

PHP Versions

Let’s take a look at the different versions of PHP, their release years, and the key features they introduced:

To learn more about it follow the article - PHP Versions

PHP vs Other Programming Languages

There are several alternatives to PHP. Some of them are Python and JavaScript. So, below is the difference between PHP, Python and JS and how they work separately.

To start your coding journey in PHP you can follow PHP Tutorial