// four possible unique names, for instances of the script... 2-3 of them get the same file name.. WHY !?

do {
  $fileName = $_SERVER['DOCUMENT_ROOT'].'/test'.mt_rand(0,3).'.txt';
  $fileHandle = @fopen($fileName,'x');

  echo $fileName.'<br>';

} while ($fileHandle === false);

echo '^ this is it<br>';
		
sleep(10); // increase running time of the script to force collisions with the other instances