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

Your own solution is perfectly fine.

preg_match uses Perl-like regular expressions, in which the character class \w defined to match exactly what you need:

\w - Match a "word" character (alphanumeric plus "_")

(source)