How can nested if statements affect the functionality of form data processing in PHP?

Nested if statements in form data processing can lead to overly complex and difficult-to-maintain code. To avoid this issue, it's recommended to use alternative approaches such as switch statements or separate functions to handle different conditions. By organizing the code in a more structured manner, it becomes easier to debug, modify, and expand the functionality of the form data processing.

// Example of using switch statements to handle form data processing
switch ($_POST['action']) {
    case 'submit':
        // Process form submission
        break;
    case 'update':
        // Process form update
        break;
    default:
        // Handle other actions or errors
        break;
}