🌐 Server-side scripting for dynamic websites
PHP (Hypertext Preprocessor) is a popular server-side scripting language designed to build dynamic web pages and web applications. It runs on the server, generating HTML content that browsers can display, making websites interactive and data-driven.
In this introduction, you’ll learn what PHP is, its primary uses, and how it interacts with web servers to deliver web content.
📁 What is PHP Used For?
- Generating dynamic HTML content based on user input or database data
- Handling form submissions and user authentication
- Managing sessions and cookies
- Interacting with databases (MySQL, PostgreSQL, etc.)
- Building complete web applications and APIs
- Running command-line scripts and automation tasks
🧱 PHP Basics
PHP code is embedded within HTML and executed on the server before the page is sent to the client. PHP scripts can generate HTML, perform calculations, access databases, and more.
🔹 How PHP Works with a Web Server
| Step | Description |
|---|---|
| 1. Client Requests a PHP Page | User’s browser sends an HTTP request to the web server for a .php file |
| 2. Server Receives the Request | The web server recognizes the .php extension and passes the request to the PHP engine |
| 3. PHP Engine Processes Code | PHP executes the script, which may include database queries, calculations, or generating HTML |
| 4. Server Sends Response | The output (usually HTML or JSON) generated by PHP is sent back to the browser |
| 5. Browser Renders the Page | The browser displays the HTML content as a webpage |
📌 PHP Code Example
<?php
echo "<h1>Welcome to my website!</h1>";
$name = "Alice";
echo "<p>Hello, $name! Today is " . date('l') . ".</p>";
?>
- This PHP code runs on the server, generating HTML sent to the browser.
- The user never sees the PHP code — only the resulting HTML.
🔎 Important Concepts
| Concept | Description |
|---|---|
| Server-side scripting | Code runs on the server, not the client |
| Embedding PHP in HTML | PHP code is placed within <?php ... ?> tags |
| Dynamic content | Pages change based on data or user input |
| Interpreted language | PHP code is executed line-by-line at runtime |
| Stateless | Each request is independent, sessions track user state |
🧩 Web Server and PHP Integration
- Common web servers running PHP include Apache, Nginx, and Microsoft IIS.
- PHP can be run as a module integrated into the web server or as a separate process (FastCGI).
- The web server routes PHP requests to the PHP interpreter, which processes the scripts.
💡 How PHP Differs from Client-Side Languages
- PHP runs before the page is sent to the browser, so the client only receives the resulting HTML/JS/CSS.
- Client-side languages like JavaScript run in the browser after the page loads.
- PHP can interact directly with the server’s filesystem, databases, and environment securely.
📚 Summary Table
| Feature | Description |
|---|---|
| Language Type | Server-side scripting language |
| Runs On | Web server |
| Output | Usually HTML/JSON |
| Execution Time | At request time on the server |
| Interaction | Works with databases, filesystems, web servers |
| Common Uses | Dynamic websites, forms, APIs |
🧠 Best Practices
✅ Keep PHP logic separate from HTML layout using templates or frameworks
✅ Sanitize user input to prevent security risks (SQL injection, XSS)
✅ Use modern PHP versions for improved performance and security
✅ Employ error handling and logging for maintainability
✅ Use sessions and cookies carefully to manage user state
🔜 What’s Next?
PHP remains a cornerstone of web development. Learning PHP opens the door to popular platforms like WordPress, Drupal, and Laravel. Try creating a simple dynamic site or API with PHP in our PHP & MYSQL Essentials course!