Courses/PHP/Introduction to PHP

Lesson 1 • Beginner

Introduction to PHP 🐘

Learn what PHP is, how it runs on the server, and why it powers over 77% of the web — from WordPress to Facebook.

What You'll Learn in This Lesson

• What PHP is and why it's the most popular server-side language
• How server-side code differs from client-side JavaScript
• The request-response cycle: browser → server → PHP → HTML → browser
• PHP syntax basics: echo, variables, comments, and string concatenation
• Setting up your PHP development environment

Note: PHP runs on a server, not in the browser. Our examples simulate PHP logic using JavaScript. To run real PHP, install PHP and use php -S localhost:8000 to start a local server.

🎯 Real-World Analogy: Think of PHP like a kitchen in a restaurant. The customer (browser) orders a dish (requests a page). The kitchen (PHP on the server) prepares the food (processes code), and the waiter (web server) delivers the finished plate (HTML) to the customer. The customer never sees the kitchen — they only see the final dish.

1️⃣ What is PHP?

PHP (Hypertext Preprocessor) is a server-side scripting language designed for web development. Unlike JavaScript which runs in the browser, PHP runs on the web server and generates HTML that gets sent to the user.

Feature	Details
Created	1995 by Rasmus Lerdorf
Latest Version	PHP 8.3 (2024)
Market Share	77% of websites with known server-side language
Famous Users	WordPress, Wikipedia, Facebook, Slack
File Extension	.php

2️⃣ PHP Syntax Basics

PHP code is written inside <?php ?> tags and can be embedded directly in HTML files:

<!DOCTYPE html>
<html>
<body>
  <h1>Welcome</h1>
  <?php
    $name = "Alice";
    echo "<p>Hello, $name!</p>";
  ?>
</body>
</html>

Key syntax rules:

Every statement ends with a semicolon ;
Variables always start with a dollar sign $
Strings are concatenated with the dot operator . not +
echo outputs text to the page

Try It: Your First PHP Script

See PHP basics — variables, echo, comments, and string concatenation (simulated in JavaScript)

Try it Yourself »

JavaScript

// PHP Introduction — Simulated in JavaScript
// In real PHP, code runs on the server inside <?php ?> tags

console.log("=== Your First PHP Script ===");
console.log();

// In PHP, you use 'echo' to output text
// echo "Hello, World!";
console.log("Hello, World!");
console.log();

// PHP can mix with HTML on the server
console.log("=== How PHP Embeds in HTML ===");
console.log();
console.log("<!DOCTYPE html>");
console.log("<html>");
console.log("<body>");
console.log("  <h1>My First PHP Page</h
...

3️⃣ How PHP Works

PHP follows a request → process → response cycle:

Browser → HTTP Request → Web Server → PHP Interpreter
                                            ↓
Browser ← HTML Response ← Web Server ← Generated HTML

💡

Pro Tip: The user never sees your PHP code — only the HTML output. This is why PHP is great for hiding business logic and database passwords.

Try It: How PHP Works (Server-Side)

Understand the request-response cycle and see PHP vs JavaScript compared

Try it Yourself »

JavaScript

// How PHP Works — Server-Side Execution
console.log("=== How PHP Works: Step by Step ===");
console.log();

// Simulate the request-response cycle
console.log("1️⃣ User types: www.example.com/index.php");
console.log("   → Browser sends HTTP request to server");
console.log();

console.log("2️⃣ Web server (Apache/Nginx) receives the request");
console.log("   → Finds index.php file on disk");
console.log("   → Passes it to the PHP interpreter");
console.log();

console.log("3️⃣ PHP interpreter 
...

4️⃣ Setting Up PHP

Three ways to start coding PHP:

Built-in Server (Easiest)
php -S localhost:8000 — no Apache needed!

XAMPP/MAMP — installs Apache + PHP + MySQL in one click

Docker — docker run -p 8080:80 php:8.3-apache

⚠️ Common Mistakes

⚠️

Forgetting the semicolon — every PHP statement must end with ;

⚠️

Missing the $ on variables — PHP requires $name, not just name

⚠️

Using + for string concatenation — PHP uses the . dot operator

💡

Pro Tip: Enable error reporting with error_reporting(E_ALL) during development to catch mistakes early.

📋 Quick Reference — PHP Basics

Syntax	Example	Description
echo	echo "Hello";	Output text
$variable	$name = "Alice";	Declare variable
. (dot)	"Hi " . $name	Concatenate strings
//	// comment	Single-line comment
<?php ?>	<?php echo "Hi"; ?>	PHP opening/closing tags

🎉 Lesson Complete!

You now understand what PHP is and how it works on the server! Next, dive into PHP variables and data types.