Metoda 1:

function trunc($phrase, $max_words) {
   $phrase_array = explode(' ',$phrase);
   if(count($phrase_array) > $max_words && $max_words > 0)
      $phrase = implode(' ',array_slice($phrase_array, 0, $max_words)).'...';
   return $phrase;
}

Metoda 2:

function limit_words($words, $limit, $append = ' …') {
       // Add 1 to the specified limit becuase arrays start at 0
       $limit = $limit+1;
       // Store each individual word as an array element
       // Up to the limit
       $words = explode(' ', $words, $limit);
       // Shorten the array by 1 because that final element will be the sum of all the words after the limit
       array_pop($words);
       // Implode the array for output, and append an ellipse
       $words = implode(' ', $words) . $append;
       // Return the result
       return $words;
}