[SOLVED] Whitelist problem for strings

[scuff]

Okay, I'm creating a login and I want to create a whitelist for characters allowed in their account name instead of using a blacklist to block every single alt code etc... So I was looking online and I found this:

if(preg_match("/[A-Za-z0-9]/",$string)) { 
echo "The string '$string' contains only letters and numbers"; 
}

But it only returns false if the string is like "#######" and it returns true if it's "fdsdfs#f" is there a way to return true even if there is only one wrong character? Thanks!

[lemmin]

Try like this:

$uname = "fdsdfs#f";
if(!preg_match("/[A-Za-z0-9]{".strlen($uname)."}/", $uname))
echo "Bad character in Username!";

[scuff]

Wow, amazing! Thanks!!!!!