Introduction & Setup

PHP is one of the most widely used programming languages on the web. It powers everything from small personal blogs to massive platforms like WordPress, Wikipedia, and Facebook's early stack. This guide takes you from zero to building a complete web application -- step by step, assuming no prior PHP experience.

How this guide is structured

Part	Chapters	What you will learn
1 -- Language Basics	1--6	Install PHP, variables, types, operators, control flow, functions, arrays
2 -- Web Fundamentals	7	HTML forms, GET/POST, input validation, superglobals
3 -- Object-Oriented PHP	8--9	Classes, inheritance, interfaces, traits, namespaces
4 -- Practical Skills	10--14	Error handling, files, databases, sessions, Composer
5 -- Modern PHP & Full Project	15--17	PHP 8 features, building a web app, practice projects

By the end you will understand how PHP works, how to build dynamic web pages, and how to structure a real application.

What is PHP?

PHP stands for PHP: Hypertext Preprocessor (a recursive acronym). It is a server-side scripting language, which means it runs on a server and produces output -- usually HTML -- that gets sent to the browser.

Here is the key idea: when you visit a website, your browser does not run PHP. The server runs PHP, generates HTML, and sends that HTML to your browser.

This is different from JavaScript, which runs directly in the browser. PHP runs before the page reaches the browser.

Why learn PHP?

• Huge ecosystem -- PHP powers roughly 75% of all websites with a known server-side language (mostly through WordPress, but also Laravel, Symfony, Drupal, and many others)
• Easy to start -- you can write a PHP file, run one command, and see results in your browser
• Mature and stable -- PHP has been around since 1995 and has evolved significantly, especially with PHP 8
• Great documentation -- php.net has one of the best language references on the web
• Jobs -- there is strong demand for PHP developers, particularly in the Laravel and WordPress ecosystems

A brief history

Year	Version	Milestone
1995	PHP 1	Created by Rasmus Lerdorf as "Personal Home Page Tools"
2004	PHP 5	Introduced proper object-oriented programming
2015	PHP 7	Massive performance improvements (2x faster), scalar type hints
2020	PHP 8.0	JIT compiler, union types, named arguments, match expression
2023	PHP 8.3	Typed class constants, json_validate(), #[Override] attribute
2024	PHP 8.4	Property hooks, asymmetric visibility, lazy objects

PHP 6 was planned but never released. The jump from 5 to 7 reflected a clean break with major performance gains.

How the web works -- a quick primer

Before we install PHP, let's make sure you understand the basics of how the web works. If you already know this, skip ahead to Prerequisites.

Clients and servers

The web is a conversation between clients and servers:

• A client is usually your web browser (Chrome, Firefox, Safari). It sends requests -- "give me this page."
• A server is a computer running software that listens for those requests and sends back responses -- usually HTML, CSS, JavaScript, images, or JSON.

Static vs dynamic websites

• A static website serves the same files to everyone. The server just hands over an HTML file as-is.
• A dynamic website generates pages on the fly. The server runs code (like PHP) to build the HTML before sending it.

PHP is how you make websites dynamic. For example, a PHP page can:

• Show different content depending on who is logged in
• Pull data from a database and display it
• Process a form submission and store the results

What happens when you visit a PHP page

1. You type http://example.com/profile.php in your browser
2. Your browser sends an HTTP request to the server at example.com
3. The server sees the .php extension and passes the file to the PHP interpreter
4. PHP executes the code in profile.php -- maybe it queries a database, checks a session, etc.
5. PHP produces HTML output
6. The server sends that HTML back to your browser
7. Your browser renders the page -- it has no idea PHP was involved

The browser never sees your PHP code. It only sees the HTML that PHP produced.

Prerequisites

Before we start, make sure you have:

• A computer running macOS, Linux, or Windows
• A text editor -- VS Code is recommended (free, great PHP support with extensions)
• A terminal -- Terminal on macOS, any terminal emulator on Linux, or Windows Terminal / PowerShell on Windows
• Basic HTML knowledge -- you should know what <h1>, <p>, <form>, and <a> tags do

You do not need:

• Prior programming experience (though it helps)
• A web server like Apache or Nginx (PHP has a built-in development server)
• A database (we add one in chapter 12)

Installing PHP

macOS

The easiest way is with Homebrew:

brew install php

Verify the installation:

php --version

You should see something like PHP 8.3.x or PHP 8.4.x.

Note: macOS used to ship with PHP pre-installed, but Apple removed it in macOS Monterey (12.0). You need to install it yourself now.

Linux (Ubuntu / Debian)

sudo apt update
sudo apt install php php-cli php-common

Verify:

php --version

For other distributions, use your package manager (dnf on Fedora, pacman on Arch, etc.).

Windows

The simplest option is to download PHP from windows.php.net:

1. Download the latest VS16 x64 Thread Safe zip
2. Extract it to C:\php
3. Add C:\php to your system PATH environment variable
4. Open a new terminal and run php --version

Alternatively, install XAMPP which bundles PHP, Apache, and MySQL -- but for this guide, standalone PHP is enough.

Tip: On Windows, you can also use WSL (Windows Subsystem for Linux) and follow the Linux instructions. This is often easier for development.

Your first PHP script

Create a new file called hello.php in any directory. Open it in your editor and type:

<?php

echo 'Hello, World!';

Let's break this down:

• <?php -- this is the opening tag. It tells the server "everything after this is PHP code." Every PHP file starts with this tag.
• echo -- this is a PHP command that outputs text. Think of it as "print to the screen."
• 'Hello, World!' -- this is a string (a piece of text). Single quotes wrap the text.
• ; -- every PHP statement ends with a semicolon. This is not optional -- forgetting it is the most common beginner mistake.

Running it from the terminal

Open your terminal, navigate to the directory where you saved hello.php, and run:

php hello.php

You should see:

Hello, World!

Congratulations -- you just ran your first PHP script.

Running it in the browser

PHP's real power is generating web pages. PHP ships with a built-in development server. In your terminal, navigate to the directory containing hello.php and run:

php -S localhost:8000

This starts a web server on port 8000. Now open your browser and go to:

http://localhost:8000/hello.php

You should see "Hello, World!" in your browser. The terminal will show a log line for each request.

Important: The built-in server is for development only. Never use it in production. We cover proper deployment options in chapter 16.

Press Ctrl+C in the terminal to stop the server.

Mixing PHP and HTML

One of PHP's strengths is that you can embed PHP directly inside HTML. Create a file called greeting.php:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>My First PHP Page</title>
</head>
<body>
    <h1>Welcome!</h1>
    <p>The current date is: <?php echo date('Y-m-d'); ?></p>
    <p>PHP version: <?php echo phpversion(); ?></p>
</body>
</html>

Start the built-in server again (php -S localhost:8000) and visit http://localhost:8000/greeting.php. You will see an HTML page with today's date and your PHP version filled in dynamically.

Notice how PHP code lives inside <?php ... ?> tags. Everything outside those tags is treated as plain HTML and sent to the browser as-is. The PHP parts are executed on the server and replaced with their output.

PHP on the command line

PHP is not limited to web pages. You can use it as a general-purpose scripting language from the terminal. Create a file called info.php:

<?php

echo 'PHP version: ' . phpversion() . "\n";
echo 'Operating system: ' . PHP_OS . "\n";
echo 'Current directory: ' . getcwd() . "\n";

Run it:

php info.php

This is called CLI mode (Command Line Interface). It is useful for:

• Automation scripts
• Data processing
• Cron jobs
• Testing snippets quickly

Throughout this guide, we will use both CLI mode and the built-in web server.

The PHP request lifecycle

Understanding how PHP processes a web request helps you reason about your code later:

The last step is important: PHP starts fresh on every request. Unlike Node.js or Java, PHP does not keep a long-running process in memory. Each request is independent. Variables, objects, and connections are created, used, and then destroyed. This "shared-nothing" architecture makes PHP simple to reason about but means you need sessions or databases to persist data between requests (chapters 12--13).

Setting up your project folder

For the rest of this guide, create a dedicated folder for your PHP learning projects:

mkdir php-guide
cd php-guide

Move your hello.php and greeting.php files into this folder. Whenever you see code examples in this guide, create them inside this directory.

Tip: Start the built-in server from this folder (php -S localhost:8000) and leave it running in a terminal tab while you work through the chapters. Every new .php file you create will be instantly accessible in your browser.

Editor setup

If you use VS Code, install these extensions for a better PHP experience:

Extension	What it does
PHP Intelephense	Autocompletion, go-to-definition, diagnostics
PHP Debug (by Xdebug)	Step-through debugging with Xdebug
EditorConfig for VS Code	Consistent formatting across editors

You do not need any of these to follow the guide, but they make writing PHP much more pleasant.

Summary

• PHP is a server-side language -- it runs on the server and sends HTML to the browser
• The browser never sees your PHP code, only the output
• You installed PHP and verified it with php --version
• You wrote your first script with echo and ran it from the terminal
• You started PHP's built-in development server with php -S localhost:8000
• You can mix PHP and HTML in the same file using <?php ... ?> tags
• PHP starts fresh on every request -- nothing persists in memory between requests

Next up: Variables & Data Types -- declaring variables, working with strings and numbers, understanding PHP's type system, and inspecting values with var_dump().