YA: Sampling a String at a Space WOC

<?php

/*    Simple function to sample a string, at a space.  Default Length is 80   */
function sample($string, $length=80){
    $string = substr($string, 0, $length);
    return substr($string, 0, strrpos($string, ' '));
}
$block = "This is some string. I think it needs to continue for a while, but I'm not entirely sure where to cut it. So I think I will simply keep adding to it, while not counting the neccessary characters for the length. Knowing this would allow me to know when to cut the string.";
$sample = sample($block);
echo $sample . '<br>';
echo 'Strlen: ' . strlen($sample) . '<br>';
$sample2 = sample($block, 120);
echo $sample2 . '<br>';
echo 'Strlen: ' . strlen($sample2) . '<br>';
?>