Restricting/disallowing username characters with eregi

Tad

Okay... for usernames at my site, I'm looking to restrict specific characters. I've sort of been messing around with eregi and a pattern string. I can't seem to get my pattern string correct though.

What I'd like it to allow in usernames are single quotes ('), letters (upper & lowercase), numbers, underscores, hyphens (-), and spaces.

Most things I've come across when looking for help with the eregi function have to do with validating email addresses and are a little bit stricter/complicated looking than I know I need. (^{.[a-zA-Z0-9..-]+@[a-z0-9]+\.[a-z]+)} Do allowed characters just have to appear somewhere in the string? How would a space be allowed? I know I don't need the +@ stuff and whatnot since I'm not validating an email address.

bradgrafelman

My approach would probably be to look for "any character that is not in (this set of characters)".

That way, you define a list of characters you want to allow, and anything outside that will return FALSE, or not valid.

My example:

function validate_username($username) {

if(eregi('[^a-zA-Z0-9\\'_[:space:]-]', $username) === FALSE) return TRUE; else return FALSE;

}

$user = 'This_Is-1 test';
if(!validate_username($user)) die('Invalid username!'); // Does nothing (valid username)

$user = 'This_Is-1 test~';
if(!validate_username($user)) die('Invalid username!'); // Invalid username!

EDIT: Had to use a

 tag since the [code=php] tag seems to strip backslashes.

Tad

That makes sense, yeah. 🙂

Could there even be a shorter way to do it? Something like...

if (!eregi("[^a-zA-Z0-9\'_[:space:]-]", $in_username))
{
print error;
return;
}

I've been trying something like that anyway. It seems to be blocking all usernames if they have any of those instances though, so ah... not quite the right approach I think. :/