html dom中的php substr

Question

How can I use substr() in a HTML dom? I want keep all the html tags and just shorten the text.

$str = '<div><a href="http://www.weather.com">Today is a nice day</a></div>';
$part1 = preg_replace("/<a(.*?)>(.*?)<\/a>/i",substr('\\2', 0,10),$str).'...';
$part2 = preg_replace("/<a(.*?)>(.*?)<\/a>/i",'\\2',$str);
echo str_replace($part2,$part1,$str);// nothing change
// I need <div><a href="http://www.weather.com">Today is a...</a></div>

Answer 1

It could probably be a bit more robust, but this should do the trick:

$str = '<div><a href="http://www.weather.com">Today is a nice day</a></div>';
echo shortenLinks($str);

function shorten($matches) {
   $maxlen = 10;
   $str = $matches[2];
   if (strlen($str) > $maxlen) {
      return "<" . $matches[1] . ">" . substr($str, 0, $maxlen) . "...<";
   } else {
      return $matches[0];
   }
}

function shortenLinks($str) {
   $pattern = "/<(a\s+.*)>([^<]+)</";
   return preg_replace_callback($pattern, "shorten", $str);
}