patrimatic

I want my PHP code to display and handle a form. If the form hasn't been submitted it needs to display the form. If the form has been submitted but the data couldn't be validated then I want to display the same form (with the user's data intact). If the form has been submitted and the data was validated then it handles the form and prints a message. The problem I seem to be having is that I have nested conditionals that both need to execute the same code. I cant seem to wrap my head around it.