How can PHP be used to ensure data validation even if JavaScript is disabled?

When JavaScript is disabled, client-side validation cannot be relied upon to validate user input. To ensure data validation even if JavaScript is disabled, server-side validation using PHP can be implemented. This involves checking user input on the server before processing it further.

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    $email = $_POST["email"];

    // Server-side validation
    if (empty($name) || empty($email)) {
        echo "Please fill out all fields.";
    } else {
        // Process the data further
    }
}