Closing ajax function file with die() causes error and empty page

The die should be in your show_article() function. Yours is out, so the whole script is terminated. Your function should be:

function show_article(){
  $q = $_GET['getid'];
  echo strval($q);
  die;
}

or

function show_article(){
  $q = $_GET['getid'];
  exit( strval($q) );
}