How to match exact word anywhere in string with PHP regexp

Question

I want to find out if user has used the words admin or username anywhere in their possible username string.

So if user wants to use admin

Answer 1

Square brackets in a regexp are not for grouping, they're for specifying character classes; grouping is done with parentheses. You don't want to anchor the regexp with ^ and $, because that will only match at the beginning and end of the string; you want to use \b to match word boundaries.

/\b(admin|username)\b/i