Routing and URL Management

# CHAPTER 13

Routing and URL Management #

1. Introduction #

2. Learning Objectives #

• Explain the concept of a Front Controller pattern.

• Configure an Apache .htaccess file to rewrite URLs.

• Build a custom PHP Router from scratch.

• Handle dynamic URL parameters (e.g., /user/5).

3. Beginner-Friendly Explanation #

4. The Magic of .htaccess (Apache Rewrite) #

.htaccess

RewriteEngine On
# If the requested URL is not an actual physical file or folder...
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# ...send all traffic to index.php
RewriteRule ^(.*)$ index.php [QSA,L]

Now, if a user types localhost/myproject/about, Apache will silently load index.php instead of looking for an about.php file.

5. Building a Basic Router #

index.php (The Front Controller)

<?php
// Get the URL the user typed
$request = $_SERVER[&#039;REQUEST_URI'];

// Remove the base project path (adjust based on your setup)
$uri = str_replace(&#039;/myproject/', '/', $request);

// The Router Logic (Switch Statement)
switch ($uri) {
    case &#039;/':
        echo "<h1>Home Page</h1>";
        break;
    case &#039;/about':
        echo "<h1>About Us</h1>";
        // In a real app, we would include a file here: require 'views/about.php';
        break;
    case &#039;/contact':
        echo "<h1>Contact Us</h1>";
        break;
    default:
        // Handle 404 Not Found
        http_response_code(404);
        echo "<h1>404 Error: Page Not Found</h1>";
        break;
}
?>

6. Dynamic URL Parameters #

<?php
$uri = $_SERVER[&#039;REQUEST_URI'];

// Use Regular Expressions to match a pattern
// This matches "/product/ANY_NUMBER"
if (preg_match(&#039;/^\/product\/([0-9]+)$/', $uri, $matches)) {
    
    // $matches[1] will hold the number the user typed in the URL
    $product_id = $matches[1];
    
    echo "<h1>Viewing Product ID: " . $product_id . "</h1>";
    // Here, you would query the database for Product #$product_id
}
?>

7. Why Use a Router? #

1. 1. Clean URLs: /users/profile looks much better and ranks higher on Google than /profile.php?userid=5&action=view.

1. 2. Centralized Security: Because every request passes through index.php, you can put your database connection and session start code at the very top. You never have to copy-paste sessionstart() into 50 different files ever again.

1. 3. Hide File Structure: Hackers cannot guess the names of your physical server files because the URLs do not map to files anymore.

8. Backend Workflow: API Routing #

9. Best Practices #

• Use a Routing Library: While building a router from scratch is a great learning exercise, professional applications use established routing packages (like bramus/router or Laravel's built-in router) which handle complex regular expressions and HTTP methods automatically.

10. Common Mistakes #

• Forgetting the .htaccess File: If you write a beautiful index.php router, but you click a link to /about and get a server-level "404 Not Found" error, it means Apache doesn't know it's supposed to route traffic to index.php. You must configure .htaccess or the Nginx equivalent.

11. Exercises #

1. 1. Explain the "Front Controller" design pattern and how it improves application security.

12. Coding Challenges #

• Challenge: Expand the basic router switch statement to include an /admin route. If the user visits /admin, write an if statement to check if a hypothetical $SESSION['isadmin'] is true. If not, output "Access Denied."

13. MCQs with Answers #

14. Interview Questions #

• Q: Describe how you would implement a dynamic route (e.g., /user/{id}) in a custom PHP router without using a framework.

• Q: What is the Front Controller pattern, and what are the architectural benefits of funneling all web traffic through a single entry point?

15. FAQs #

16. Summary #

17. Next Chapter Recommendation #