Laravel 5.5 - Check if string contains exact words

In laravel, I have a $string and a $blacklistArray

$string = 'Cassandra is a clean word so it should pass the check';
$blacklistArray = ['ass','ball sack'];

$contains = str_contains($string, $blacklistArray); // true, contains bad word

The result of $contains is true, so this will be flagged as containing a black list word (which is not correct). This is because the name below partially contains ass

Cassandra

However, this is a partial match and Cassandra is not a bad word, so it should not be flagged. Only if a word in the string is an exact match, should it be flagged.

Any idea how to accomplish this?

$blacklistArray = array('ass','ball sack');

$string = 'Cassandra is a clean word so it should pass the check';



$matches = array();
$matchFound = preg_match_all(
                "/\b(" . implode($blacklistArray,"|") . ")\b/i", 
                $string, 
                $matches
              );

// if it find matches bad words

if ($matchFound) {
  $words = array_unique($matches[0]);
  foreach($words as $word) {

    //show bad words found
    dd($word);
  }

}