What are the best practices for combining PHP and JavaScript functionalities in form handling?

When combining PHP and JavaScript functionalities in form handling, it is important to use PHP for server-side validation and processing of form data, while using JavaScript for client-side validation and enhancing user experience. This combination ensures that data is validated both on the client-side and server-side, providing a more robust and secure form handling process.

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Server-side validation and processing
    $name = $_POST['name'];
    $email = $_POST['email'];
    
    if (empty($name) || empty($email)) {
        echo "Please fill out all fields.";
    } else {
        // Process form data
        // Insert into database, send email, etc.
        echo "Form submitted successfully!";
    }
}
?>