HTML send and receive response from PHP on same page

I Got a page that send request to PHP and PHP calculate a value and return it but i get the value in text plain on php page. I have 2 files [login to view URL] and [login to view URL], I want that [login to view URL] send and receive the calculation. Right now my project is working like this: [login to view URL] send value to php with a form and submit button but is redirecting to php and shows the value in plain text. What im trying to do is send the request on my html to php to calculate the value then return the value calculated to same html page.