A suggestion:

I was thinking that there are some functions that should exist in PHP:

1: if(eregi("[A-Z]", $string)) this could be called something like is_a2z (any name is OK, I just though about nl2br). Instead of using RegEx which is real slow when you have to check strings several times in a script a simple function like this would be of a BIG HELP. (I know of is_numeric(), but it's use will not make you sure that the string is esclusivelly alphabetic). A build-in function to detect whether a $string is entirelly made from a-z avoiding so regular expression use is really needed, I think.

2: Another thing (Less important) is that instead of using (ereg("[:alnum:]", $string)) you could just say if(!is_almun($string)), just to make (ereg("[:alnum:]", $string)) be a little lighter and easier for beginners. (few beginners use [:almun:], they usually get into writing some huge long expressions,) this would impress them a lot.

Thanks for your patience,
Maxim Maletsky