How can the isset() and empty() functions be effectively used to check for the presence of form submission data in PHP scripts?

When working with form submission data in PHP scripts, it is important to check if the data has been submitted before trying to access it to avoid errors. The isset() function can be used to check if a variable is set and not null, while the empty() function can be used to check if a variable is empty. By combining these functions, we can effectively check for the presence of form submission data in PHP scripts.

if(isset($_POST['submit'])){
    // Form data has been submitted
    if(!empty($_POST['data'])){
        // Process the form data
        $data = $_POST['data'];
        // Additional processing
    } else {
        // Handle case where form data is empty
    }
} else {
    // Form has not been submitted
}