eregi help validating a folder name

[medar]

I use the following code to validate email addresses, and am trying to change it to validate the creation of a folder that will store uploaded files.

if (!eregi("^{a-z0-9@((([a-z0-9]+[a-z0-9\-][a-z0-9]+)|[a-z0-9])+\.)+[a-z]{2,10}$",} $email)) { print "You did not enter a valid email address. Please use your browser's back button and fill out all required fields.<BR><BR>"; exit;}

I understand HOW eregi works, but all the variables in there are foreign to me. How would I change the above to check for a file name that is ONLY letters and numbers, and 16 characters or less?

IE good =

1998activeproj

IE bad =

1998activeprojects
1998-active
$active1998

Thanks for any help.

[LordShryku]

Don't need eregi. Could just use [man]strlen[/man] and [man]ctype_alnum[/man]. Would also help for better error reporting to the user. ie. "Your folder name is too long/short" and "Can only contain numbers and alphas".

[laserlight]

This matches an alphanumeric string of 1 to 16 characters inclusive, and is case-insensitive:

if (!preg_match('/^{[a-z0-9]{1,16}$/i',} $email))

An alternative would be:

setlocale(LC_CTYPE, "C"); //to ensure [a-z0-9]
if (strlen($email) <= 16 && ctype_alnum($email))

[medar]

Perfect!

Thanks to both of you, and time to read up on strlen and ctype_alnum.