PHP - How to add content from submit.

I'm having difficulty... I'm trying to create a form which has an input with a submit button which I have set with a condition onClick.

  if(isset($_POST['addEp'])) {
       echo "Button Clicked."; 
  } 

But, instead of the outcome being "button is clicked", I want to be able to add an entry onto a my current form and add a new text input every time the button is clicked.

Thanks in advance.