← Back to Curriculum

PHP Introduction

📚 Lesson 1 of 12 ⏱️ 20 min

PHP Introduction

20 min

PHP (Hypertext Preprocessor) is a server-side scripting language designed for web development. Created by Rasmus Lerdorf in 1994, PHP has evolved into a powerful, feature-rich language used by millions of websites including Facebook, Wikipedia, and WordPress. PHP is particularly well-suited for server-side web development, handling form processing, database interactions, and dynamic content generation.

PHP code is embedded within HTML and executed on the server before the page is sent to the browser. This server-side execution means PHP can access databases, file systems, and other server resources that JavaScript cannot. The server processes PHP code, generates HTML, and sends only the HTML to the client. This architecture enables dynamic, data-driven websites.

PHP files have a .php extension and can contain HTML, CSS, JavaScript, and PHP code mixed together. PHP code is enclosed in `<?php ?>` tags, allowing seamless integration with HTML. Modern PHP development often separates logic from presentation using frameworks or templating engines, but understanding basic PHP-in-HTML is fundamental. PHP's flexibility makes it easy to add dynamic functionality to static pages.

PHP is an interpreted language, meaning code is executed directly without compilation. This enables rapid development and easy deployment—just upload PHP files to a web server. Modern PHP (7.4+) includes a JIT compiler for improved performance. PHP's syntax is similar to C, Java, and Perl, making it accessible to developers familiar with those languages.

PHP's extensive standard library includes functions for string manipulation, array operations, file handling, database connectivity, and more. The language supports object-oriented programming, functional programming, and procedural programming styles. Understanding PHP's capabilities and when to use different programming paradigms helps you write effective PHP code.

Setting up a PHP development environment typically involves installing a web server (Apache/Nginx), PHP, and optionally a database (MySQL/PostgreSQL). Tools like XAMPP, WAMP, or Docker provide complete development environments. Modern PHP development uses Composer for dependency management and follows PSR standards for code organization. Understanding the PHP ecosystem helps you build maintainable applications.

Key Concepts

  • PHP is a server-side scripting language for web development.
  • PHP code executes on the server before sending HTML to browser.
  • PHP files can mix PHP code with HTML, CSS, and JavaScript.
  • PHP is interpreted (no compilation step required).
  • PHP has extensive built-in functions for web development tasks.

Learning Objectives

Master

  • Setting up PHP development environment
  • Writing basic PHP scripts embedded in HTML
  • Understanding server-side vs client-side execution
  • Using PHP's built-in functions

Develop

  • Understanding web application architecture
  • Appreciating PHP's role in dynamic web development
  • Setting up efficient PHP development workflows

Tips

  • Use <?php ?> tags to embed PHP code in HTML.
  • Always use <?php opening tag (not <? short tag) for portability.
  • Test PHP code on a local server before deploying.
  • Use error_reporting(E_ALL) during development to catch errors.

Common Pitfalls

  • Not running PHP on a server (PHP requires a web server, not just opening files).
  • Mixing PHP syntax with other languages, causing parse errors.
  • Not escaping output, causing XSS vulnerabilities.
  • Using deprecated PHP features that won't work in newer versions.

Summary

  • PHP is a server-side scripting language for web development.
  • PHP code executes on the server, generating HTML for the browser.
  • PHP files can contain mixed HTML and PHP code.
  • Understanding PHP is essential for server-side web development.

Exercise

Create a simple PHP script that displays 'Hello, World!' and the current date.

<!DOCTYPE html>
<html>
<head>
    <title>PHP Hello World</title>
</head>
<body>
    <h1><?php echo "Hello, World!"; ?></h1>
    <p>Today is: <?php echo date('Y-m-d H:i:s'); ?></p>
</body>
</html>

Exercise Tips

  • Use <?= as shorthand for <?php echo (PHP 5.4+): <?= 'Hello' ?>.
  • Try different date formats: date('l, F j, Y') for 'Monday, January 1, 2024'.
  • Add variables: <?php $name = 'World'; echo "Hello, $name!"; ?>.
  • Use htmlspecialchars() when outputting user input to prevent XSS.

Code Editor

Output