Retrieve a substring of the text by limiting the word count. Taken from Omeka and slightly modified.

snippet_by_word_count.php

<?php
/**
 * Retrieve a substring of the text by limiting the word count.
 * Note: it strips the HTML tags from the text before getting the snippet
 * 
 * @param string $text The text string to snip.
 * @param integer $maxWords The number of words to return from the text.
 * @param string $endString Optional string to use on the end of the 
 * returned snippet. Uses '&hellip;.' by default.
 * @return string
 **/
function snippet_by_word_count($text, $maxWords = 20, $endString = '&hellip;.')
{
    // strip html tags from the text
    $text = strip_formatting($text);
    
    if ($maxWords > 0) {
        $textArray = explode(' ', $text);
        if (count($textArray) > $maxWords) {
            $text = implode(' ', array_slice($textArray, 0, $maxWords)) . $endString;            
        }
    } else {
        return '';
    }
    return $text;
}