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 , 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

Answer 2

Just look for words using word boundaries:

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

and if there is a match return error eg

if (preg_match('/\b(?:admin|username)\b/i', $input)) {
    die("Invalid Input");
}

Answer 3

Try the below snippet to keep your list of words in Array .

$input = "im username ";
$spam_words = array("admin", "username");
$expression = '/\b(?:' . implode($spam_words, "|") . ')\b/i';

if (preg_match($expression, $input)) {
  die("Username contains invalid value");
}
else {
  echo "Congrats! is valid input";
}

Working Fiddle URL:
http://sandbox.onlinephpfunctions.com/code/6f8e806683c45249338090b49ae9cd001851af49

Answer 4

This might be the pattern that you're looking for:

'#(^|\s){1}('. $needle .')($|\s|,|\.){1}#i'

Some details depend on the restrictions that you want to apply.