Hello @kartik,
It seems that you need scandir instead of glob, as glob can't see unix hidden files.
<?php
$pid = basename($_GET["prodref"]); //let's sanitize it a bit
$dir = "/assets/$pid/v";
if (is_dir_empty($dir)) {
  echo "the folder is empty"; 
}else{
  echo "the folder is NOT empty";
}
function is_dir_empty($dir) {
  if (!is_readable($dir)) return NULL; 
  return (count(scandir($dir)) == 2);
}
?>
Hope it works!!
Thank You!!