Depends what you are doing. The second method is more complicated (you can make a mistake much easier), and the first meets the eye. However with the first method you can't put there any value from association array nor call a function. That means you can't write:
<a href="<?echo "viewmenu.php?fromwhere=$_POST['fromwhere']&date=date('Y-m-d')";?> where with second way you may do it: <a href="<?echo "viewmenu.php?fromwhere=".$_POST['fromwhere']."&date=".date('Y-m-d');?>
It's really up to you which method you use. I use both - when I can I use first, when it's not possible I use dots.