In what scenarios should JavaScript be preferred over PHP for handling user interactions and data manipulation on a webpage?

JavaScript should be preferred over PHP for handling user interactions and data manipulation on a webpage when real-time interactions are required without page reloads, such as form validation, dynamic content updates, and animations. JavaScript runs on the client-side, allowing for faster responses and a more interactive user experience compared to PHP, which requires server-side processing.

// Example PHP code for form validation
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    $email = $_POST["email"];
    
    if (empty($name) || empty($email)) {
        echo "Please fill out all fields.";
    } else {
        // Process form data
    }
}