I think its because the SQL statement needs the dates inside the quotation marks. Try
$where .= " AND post_date >= '$s' AND post_date <= '$e'";
That should work, otherwise, try
$where .= " AND post_date >= '".$s."' AND post_date <= '".$e."'";
I think its because the SQL statement needs the dates inside the quotation marks. Try
$where .= " AND post_date >= '$s' AND post_date <= '$e'";
That should work, otherwise, try
$where .= " AND post_date >= '".$s."' AND post_date <= '".$e."'";