php regular expression to match string if NOT in an HTML tag

Using regex: php regular expression to match string if NOT in an HTML tag on newest questions tagged regex – Stack Overflow

I’m trying to solve this bug in Drupal’s Hashtags module: http://drupal.org/node/1718154

I’ve got this function that matches every word in my text that is prefixed by “#”, like #tag:

function hashtags_get_tags($text) {
    $tags_list = array();
    $pattern = "/#[0-9A-Za-z_]+/";
    preg_match_all($pattern, $text, $tags_list);
    $result = implode(',', $tags_list[0]);
    return $result;
    }

I need to ignore internal links in pages, such as <a href="#reference">link</a>, or, more in general, any word prefixed by # that appears inside an HTML tag (so preceeded by < and followed by >).

Any idea how can I achieve this?

source: http://stackoverflow.com/questions/11856858/php-regular-expression-to-match-string-if-not-in-an-html-tag
Using regex: using-regex