stepping through alphabet

I am using PHP 4.3.4 and am trying to come up with a function that will step through the alphabet so that I get a menu/links that can be clicked on like below: <a href="?action=alphabet&letter=A">A</a> <a href="?action=alphabet&letter=B">B</a> <a href="?action=alphabet&letter=C">C</a> etc........... I am sure that this has been done and is probably pretty easy. Any help here would be appreciated. I know that I could just create a link for each letter, but I would like to learn to do this so that I can make code shorter. Putting each letter into an array and steping through the array will work, but can it be done by telling a loop to start at A and end at Z? Thanks Steve