NEED TO SORT CHARACTERS!! HELP!!

[Anon]

I have a string ex."rRaAtT" or similar and I want to make it "AaRrTt", sorted in alphabetical order where an uppercase letter goes in front of a lower case letter.

Please help!!!

[Anon]

And PHP's functions ride to the rescue again...

$string='HushPuppies';
$array=preg_split('//',$string,-1,PREG_SPLIT_NO_EMPTY);
natcasesort($array);
$string=join('',$array);

But really, I'm getting more and more curious about what all these string manipulations are in aid of...

[Anon]

Thats for my biology class. If I make a program that counts some thing i'll get an 'A' for the marking period and a recomendation. Thanks a lot!