PHP: A function to return the first n words from a string

function shorten_string($string, $wordsreturned)
/*  Returns the first $wordsreturned out of $string.  If string
contains fewer words than $wordsreturned, the entire string
is returned.
*/
{
$retval = $string;      //  Just in case of a problem

$array = explode(" ", $string);
if (count($array)<=$wordsreturned)
/*  Already short enough, return the whole thing
*/
{
$retval = $string;
}
else
/*  Need to chop of some words
*/
{
array_splice($array, $wordsreturned);
$retval = implode(" ", $array)." ...";
}
return $retval;
//Source: http://www.nutt.net/2004/12/29/php-a-function-to-return-the-first-n-words-from-a-string/
}