PHP限制文本字符串不包括html标签？

这是对我不起作用的：

<?php
 $string = 'I have a dog and his name is <a href="http://www.jackismydog.com">Jack</a> and I love him very much because he\'s my favorite dog in the whole wide world and nothing could make me not love him, I think.';
 $limited = substr($string, 0, 100).'...';
 echo $string;
?>

我想将可见文本限制为 100 个字符，但使用substr()还包括限制中的不可见文本（<a href="http://www.jackismydog.com"> and </a>) 占用了 100 个可用字符中的 41 个。

有没有办法限制文本，以便链接中的“Jack”一词包含在限制中，但不包含在内<a href="http://www.jackismydog.com"> or </a>?

编辑： 我想将链接保留在字符串中，只是不将其长度计入限制。

截断 HTML 代码中单词的函数：

//+ Jonas Raoni Soares Silva
//@ http://jsfromhell.com
function truncate($text, $length, $suffix = '…', $isHTML = true) {
    $i = 0;
    $simpleTags=array('br'=>true,'hr'=>true,'input'=>true,'image'=>true,'link'=>true,'meta'=>true);
    $tags = array();
    if($isHTML){
        preg_match_all('/<[^>]+>([^<]*)/', $text, $m, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
        foreach($m as $o){
            if($o[0][1] - $i >= $length)
                break;
            $t = substr(strtok($o[0][0], " \t\n\r\0\x0B>"), 1);
            // test if the tag is unpaired, then we mustn't save them
            if($t[0] != '/' && (!isset($simpleTags[$t])))
                $tags[] = $t;
            elseif(end($tags) == substr($t, 1))
                array_pop($tags);
            $i += $o[1][1] - $o[0][1];
        }
    }

    // output without closing tags
    $output = substr($text, 0, $length = min(strlen($text),  $length + $i));
    // closing tags
    $output2 = (count($tags = array_reverse($tags)) ? '</' . implode('></', $tags) . '>' : '');

    // Find last space or HTML tag (solving problem with last space in HTML tag eg. <span class="new">)
    $pos = (int)end(end(preg_split('/<.*>| /', $output, -1, PREG_SPLIT_OFFSET_CAPTURE)));
    // Append closing tags to output
    $output.=$output2;

    // Get everything until last space
    $one = substr($output, 0, $pos);
    // Get the rest
    $two = substr($output, $pos, (strlen($output) - $pos));
    // Extract all tags from the last bit
    preg_match_all('/<(.*?)>/s', $two, $tags);
    // Add suffix if needed
    if (strlen($text) > $length) { $one .= $suffix; }
    // Re-attach tags
    $output = $one . implode($tags[0]);

    //added to remove  unnecessary closure
    $output = str_replace('</!-->','',$output); 

    return $output;
}

Source: http://snippets.dzone.com/posts/show/7125