What are some best practices for structuring PHP code in separate files for form processing?

When processing forms in PHP, it is best practice to separate the code into different files to improve organization and maintainability. One common approach is to have a separate file for form validation, another for form processing, and another for rendering the form. This separation of concerns helps to keep the codebase clean and easy to manage.

// form_validation.php
function validateForm($formData) {
    // Validation logic here
}

// form_processing.php
function processForm($formData) {
    // Processing logic here
}

// render_form.php
function renderForm() {
    // Form rendering logic here
}