takes a string (expecting no html) and adds   to it to prevent widows

no_widow.php

<?php

/**
 * replaces the last space in a block of text with a &nbsp; to help prevent widows
 * @param $string
 * @return string
 */
function no_widow($string)
{
    $string = trim($string);
    $line_split = preg_split('`\n`', $string);
    $rvalue = '';
    if (count($line_split) > 1) {
        foreach ($line_split as $split) {
            $rvalue .= no_widow($split) . "\n";
        }
    } else {
        $split = preg_split('`[\s]+`', $string);
        $last = array_pop($split);
        if (count($split) > 0) {
            $rvalue .= implode(' ', $split) . '&nbsp;';
        }
        $rvalue .= $last;
    }
    return $rvalue;
}