Validate username as alphanumeric with underscores

Question

On my registration page I need to validate the usernames as alphanumeric only, but also with optional underscores. I\'ve come up with this:

function validate         


        

Answer 1

try

function validate_alphanumeric_underscore($str) 
{
    return preg_match('/^[a-zA-Z0-9_]+$/',$str);
}