Javascript+ajax+php

Hi,
How can i in JavaScript run php script without returning a value ?
I need run for sample this php script

<?php
$a = 1 + 2 ;
echo '<table><tr><td>' .$a.'</td></tr></table>';
?>

Javascript is run in the browser. PHP is run on the server and sends a response back to the browser. You can run a server with PHP installed on your local machine.

Can you send me link to website with samples how can i run php script in javascript without returning a value ?