Echo each of the array value and put a </br> between them.
When the button is clicked, the arrangement of the array will be reversed so the display of array will be reversed.
Make the script repeatable, each time of click will reverse the array.
Eg: 1st click will make the array reverse but 2nd click will make the array arrangement normal again,
3rd click make the array reverse again...etc..
More Challenge: Put the whole code into only a single php page. (Input,process,output in the same page)
This was my homework back then.