Bye bye, regular expressions!
Thanks to the tidy parser, no longer do you have to rely on regular expressions to extract content from another HTML document. Rather, you can use a much more maintainable solution!

In the following example (found in the ext/tidy/examples/ directory), I use the tidy parser to extract all of the links from an arbitary HTML document

Grabbing URLs from an HTML document
<?php
    function dump_nodes(tidy_node $node, &$urls = NULL) {

        $urls = (is_array($urls)) ? $urls : array();
    
        if(isset($node->id)) {
            if($node->id == TIDY_TAG_A) {
                $urls[] = $node->attribute['href'];
                }
        }
            
        if($node->hasChildren()) {

            foreach($node->child as $c) {

                dump_nodes($c, $urls);
        
            }

        }
    
        return $urls;
        }

    $a = tidy_parse_file($_SERVER['argv'][1]);
    $a->cleanRepair();
    print_r(dump_nodes($a->html()));
?>