Re: Informing a User of an Illegal Character in a post

Basically, you want to do a regular expression to see what characters are in the username, and make none of them are illegal... I currently have the rules of 5-30 characters lowercase, numbers 0-9 and underscore (_) only I achieve this with: <? if((!preg_match("/^[a-z0-9_]*$/", $username)) OR (strlen($username) < 5) OR (strlen($username) > 30) ) { echo "username invalid -- must contain only blah blah blah"; } You could extend preg_match("/^[a-z0-9_]*$/", $username) to match more or less characters to suit your needs, but I'm no expert. [a-zA-Z0-9_-] would also include a dash (-) and uppercase chars Best advice I can give you is rather than worrying about which chars might do damage, think the other way, and only allow characters you trust. Justin on 10/01/03 1:46 AM, Vernon (vernon@comp-wiz.com) wrote: > I'm having trouble when a user post a message to a MySQL database where if a > user create a user name like 'user&user' as the & symbol is used in URLs. > Does anyone have any idea how I can inform user that they have entered and > illegal character and are there are illegal characters that I should let > them use other than '&' and '?'