Form Text Input Check String for Characters

[aenigma]

Hey, I was wondering if there was a way to make sure a string from an input box doesn't contain anything except a-z and 1-0 without checking an entire string against every character I don't want. Thanks for any help!

[mga_ka_php]

use regex

[aenigma]

Well, although that was REALLY vague, lol, I managed to read enough to figure it out. Here's what I came up with:

	if (!ereg("^[a-zA-Z0-9_]{4,16}$", $_POST["uname"])) {
	echo "Invalid Username<br>Usernames must be between 4 and 16 characters, contain only alphanumeric characters and \"_\"";
	$allchecks = 0;
}