PHP Fundamentals

Introduction to PHP & Server-Side Programming

13 min Lesson 1 of 45

Introduction to PHP & Server-Side Programming

Welcome to the world of PHP programming! In this lesson, we'll explore what PHP is, how it differs from client-side languages like HTML, CSS, and JavaScript, and why it's one of the most popular server-side programming languages in the world.

What is PHP?

PHP (Hypertext Preprocessor) is a widely-used open-source server-side scripting language designed specifically for web development. PHP code is executed on the server, generating HTML which is then sent to the client's browser.

Key Fact: PHP powers over 77% of all websites with a known server-side programming language, including major platforms like WordPress, Facebook, Wikipedia, and Slack.

Client-Side vs Server-Side Programming

Understanding the difference between client-side and server-side programming is crucial:

Client-Side (HTML, CSS, JavaScript):
- Code runs in the user's browser
- Visible to users (can view source code)
- Cannot access databases or server files
- Fast execution (no server round-trip)
- Examples: Form validation, animations, DOM manipulation

Server-Side (PHP, Python, Ruby, Node.js):
- Code runs on the web server
- Hidden from users (secure)
- Can access databases and server files
- Generates dynamic content
- Examples: User authentication, database queries, file uploads

How PHP Works

Here's the typical workflow of a PHP application:

User requests a PHP page (e.g., www.example.com/index.php)
Web server sends the request to PHP interpreter
PHP interpreter executes the PHP code
PHP generates HTML output
Server sends the HTML to the user's browser
Browser displays the page

Tip: Users never see your PHP code - they only see the HTML output that PHP generates. This makes PHP perfect for protecting sensitive logic and data.

What Can PHP Do?

PHP is incredibly versatile and can handle a wide range of tasks:

Generate dynamic page content - Display personalized information based on user data
Create, read, update, and delete files - Manage files on the server
Collect and process form data - Handle user input securely
Work with databases - Store and retrieve data from MySQL, PostgreSQL, etc.
Send and receive cookies - Track user sessions and preferences
Control user access - Implement authentication and authorization
Encrypt data - Secure sensitive information
Generate images and PDFs - Create dynamic graphics and documents

Why Learn PHP?

✓ Easy to Learn: Simple syntax similar to C and Perl
✓ Free & Open Source: No licensing costs
✓ Cross-Platform: Runs on Windows, Linux, macOS
✓ Database Support: Works with MySQL, PostgreSQL, Oracle, etc.
✓ Large Community: Extensive documentation and support
✓ Job Opportunities: High demand for PHP developers
✓ Frameworks: Laravel, Symfony, CodeIgniter for rapid development

PHP Version History

Understanding PHP's evolution helps you appreciate its current capabilities:

PHP 4 (2000): Introduced Zend Engine
PHP 5 (2004): Object-oriented programming (OOP)
PHP 7 (2015): 2x performance improvement, type declarations
PHP 8 (2020): JIT compiler, named arguments, attributes
PHP 8.3 (2023): Latest stable version with modern features

Important: PHP versions below 7.4 are no longer supported. Always use PHP 8.0 or higher for new projects to ensure security updates and modern features.

Your First Look at PHP Code

Here's a simple example of PHP code (don't worry if you don't understand it yet):

<?php
    echo "Hello, World!";
    $name = "John";
    echo "Welcome, " . $name;
?>

This code outputs:

Hello, World!
Welcome, John

What You'll Need

To start developing with PHP, you'll need:

A Web Server: Apache or Nginx
PHP Interpreter: PHP 8.0 or higher
A Database (optional): MySQL or MariaDB
A Code Editor: VS Code, PhpStorm, or Sublime Text

Recommendation: Use XAMPP (Windows/Mac) or LAMP (Linux) - these are pre-configured packages that include Apache, PHP, and MySQL, making setup incredibly easy.

PHP in the Real World

Major platforms built with PHP:

WordPress: 43% of all websites
Facebook: Started with PHP, still uses it
Wikipedia: Powered by PHP
Slack: Backend built with PHP
Mailchimp: Email marketing platform
Etsy: E-commerce marketplace

Reflection Exercise:

Think About:

What's the main difference between client-side and server-side code?
Why is PHP code hidden from users while HTML is visible?
Name three things you can do with PHP that you can't do with HTML/CSS/JavaScript alone.

Answer:

Client-side code runs in the browser; server-side code runs on the web server before sending HTML to the browser.
PHP executes on the server and only sends HTML output to the browser, keeping business logic and sensitive operations secure.
Access databases, read/write server files, process sensitive data securely.

Summary

In this lesson, you learned:

PHP is a server-side scripting language for web development
Server-side code runs on the server and is hidden from users
PHP can generate dynamic content, work with databases, and handle file operations
PHP powers major platforms and has excellent job market demand
PHP 8+ offers modern features and excellent performance

Next Up: In the next lesson, we'll set up your PHP development environment and write your first PHP script!