如何在字符串中的任何位置匹配精确的单词与PHP正则表达式

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, or I am admin, or my admin name or my username, as their username, I want my regexp to detect it. If he uses adminmember I can live with that, don't detect it. I also want detection to be case insensitive.

So far I got this, but it is not really working as I thought, since it will detect words that it shouldn't:

/^[admin|username]+$/i

This will match even adm, and it shouldn't. I have tried with word boundaries, but I couldn't make it work either, maybe I did something wrong. As you can see in my question I would like to detect word admin anywhere in the string, but if it is a part of some word I can skip it.

Thanks in advance.

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