How can PHP developers improve the readability and maintainability of their code when handling different form actions like preview and submit?

To improve the readability and maintainability of PHP code when handling different form actions like preview and submit, developers can use conditional statements to separate the logic for each action. By clearly defining the actions and their corresponding code blocks, it becomes easier to understand and maintain the code.

if ($_POST['action'] == 'preview') {
    // Code for preview action
    // Display preview of form data
} elseif ($_POST['action'] == 'submit') {
    // Code for submit action
    // Process form data and save to database
} else {
    // Default action or error handling
    // Display an error message or redirect
}