What are some examples of websites that successfully track user activity in real-time using PHP?

Tracking user activity in real-time using PHP can be achieved by implementing a system that records user interactions such as page views, clicks, form submissions, etc. This data can then be stored in a database and displayed in a dashboard for analysis. One way to track user activity in real-time is by using AJAX requests to send data to the server without refreshing the page.

```php
// Sample PHP code snippet for tracking user activity in real-time using AJAX

// Include database connection
include 'db_connection.php';

// Get user activity data from AJAX request
$user_id = $_POST['user_id'];
$page_url = $_POST['page_url'];
$activity_type = $_POST['activity_type'];

// Insert user activity data into database
$sql = "INSERT INTO user_activity (user_id, page_url, activity_type, timestamp) VALUES ('$user_id', '$page_url', '$activity_type', NOW())";
$result = mysqli_query($conn, $sql);

// Check if data was successfully inserted
if ($result) {
    echo "User activity recorded successfully";
} else {
    echo "Error recording user activity";
}
```

This code snippet demonstrates how to track user activity in real-time using PHP and AJAX. It captures user data such as user ID, page URL, and activity type, then inserts this data into a database table named `user_activity`. The script also provides feedback to the user on whether the activity was recorded successfully or if there was an error.