PHP Web Features

Theory

PHP excels at web-specific tasks. It natively handles form submissions, maintains user state with sessions and cookies, and processes HTTP requests.

Form Handling

PHP automatically populates $_GET and $_POST superglobals with form data:

<!-- form.html -->
<form method="POST" action="process.php">
    <input type="text" name="username">
    <input type="submit">
</form>
 
<!-- process.php -->
<?php
$username = $_POST['username'];
echo "Hello, $username!";
?>

• $_GET — URL parameters (?key=value)
• $_POST — form body data (not visible in URL)
• $_REQUEST — combines GET and POST

Sessions

Sessions store user data across multiple page requests. The server assigns a unique session ID stored in a cookie:

session_start();
$_SESSION['user_id'] = 42;
$_SESSION['cart'] = ['item1', 'item2'];

Sessions are server-side — only the session ID is stored on the client.

Cookies

Cookies are small pieces of data stored on the client's browser:

setcookie("theme", "dark", time() + 86400 * 30);  // 30 days
echo $_COOKIE['theme'];  // "dark"

State Management Comparison

| Method | Storage | Security | Lifetime | |--------|---------|----------|----------| | GET params | URL | Low | Single request | | POST data | Request body | Medium | Single request | | Cookies | Browser | Low | Configurable | | Sessions | Server | High | Configurable |

Why this matters

Form handling, sessions, and cookies are at the core of every interactive website. From login systems to shopping carts, these PHP features let you manage user state and process input securely.

What's next

In the next lessons, you'll dive deeper into each topic with hands-on examples and exercises.

Exercises

First visit: 'Welcome! This is your first visit.' Subsequent visits: 'Welcome back! You've visited X times.'

Mini Quiz