Word限制器php删除结束逗号

I am using a word limitor from code ignitor. My database spits out a string for the homepage and since its too long to fit this code adds an '...' at the end that is linked to the corresponding page. Recently I have come across a problem in which if I have a comma in a certain place we get a ',...' which to me looks messy. So I decided to change the code in order to limit the string to a certain amount of words, at which point if the string ends in a comma after limiting, then we change the limitor amount to -1. Unfortunately the code is not working and I do not see where I am going wrong.

    // limits a string to X number of words.
    function word_limiter($str, $limit = 100, $link_end = '', $end_char = '…')
    {
        if (trim($str) == '') {
            return $str;
        }
// modified
        $cfc = preg_match('/^\s*+(?:\S++\s*+){1,' . (int) $limit . '}/', $str, $matches);
        if (substr($cfc, -1) == ',') {
            $limit_minus = $limit-1;
            preg_match('/^\s*+(?:\S++\s*+){1,' . (int) $limit_minus . '}/', $str, $matches);
        }
        if (strlen($str) == strlen($matches[0])) {
            $end_char = '';
        }
        if (empty($link_end)) {
            return rtrim($matches[0]) . $end_char;
        } else {
            $end = '<a href="'.$link_end.'">'.$end_char.'</a>'; 
            return rtrim($matches[0]) . $end;
        }

    }

You can use PHP's trim function

http://php.net/manual/en/function.trim.php

$str1 = 'a,b,c,';
$str = trim($str1, ',');

Final code:

function word_limiter($str, $limit = 100, $link_end = '', $end_char = '…')
{
    if (trim($str) == '') {
        return $str;
    }
    preg_match('/^\s*+(?:\S++\s*+){1,' . (int) $limit . '}/', $str, $matches);
    if (strlen($str) == strlen($matches[0])) {
        $end_char = '';
    }
    if (empty($link_end)) { // if link end is empty do not output a link
        return trim(rtrim($matches[0]), ',') . $end_char;
    } else {
        $end = '<a href="'.$link_end.'">'.$end_char.'</a>'; 
        return trim(rtrim($matches[0]), ',') . $end;
    }
}