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

Just look for words using word boundaries:

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

and if there is a match return error e.g.

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

Answer 2

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 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.