detecting and replacing bad words in a string

gistfile1.php

<?php
$text = 'word1 some more words. word2 and some more words';
$text = preg_replace_callback('!\w+!', 'filter_bad_words', $text);
echo $text;

function filter_bad_words($matches) {
  
  $bad_words = array(
    'word1' => 'gosh',
    'word2' => 'darn',
  );

  $replace = $bad_words[$matches[0]];
  return isset($replace) ? $replace : $matches[0];
}
?>