Script that return same response - just test communication

I need to test some android app but I depends of some thing that isn't finished yet. I send get request to site ( example http://www.test.com?a=1&b=1),开发者_开发问答 how to write script in php which always return me same thing( example a=4 ) ? I need to test communication

---

You want it to always the return the same thing, regardless of the query string you send? Just create the file and in it put

a=4

No need to use PHP for that.

If what you really meant was that you want it to echo the values from the query string.

<?php

foreach ($_GET as $key=>$value) {
  echo "$key=$value\n";
}

(obvious xss vulnerability)