// makeTeaser: makes a teaser for the number of words specified
function makeTeaser($text, $numWords) {
  $words = split(' ', $text);
  $words = array_chunk($words, $numWords);
  $output = implode(' ', $words[0]);
  $output = strip_tags($output) . '...';
  
  return $output;
}

Make an HTML Correct Teaser

textmate, drupal

HTML