Permalinks & Pingback-Problem

// let's find which post is linked to
        // FIXME: does url_to_postid() cover all these cases already?
        //        if so, then let's use it and drop the old code.
        $urltest = parse_url($pagelinkedto);
        if ($post_ID = url_to_postid($pagelinkedto)) {
            $way = 'url_to_postid()';
        } elseif (preg_match('#p/[0-9]{1,}#', $urltest['path'], $match)) {
            // the path defines the post_ID (archives/p/XXXX)
            $blah = explode('/', $match[0]);
            $post_ID = $blah[1];
            $way = 'from the path';
        }

// examine a url (supposedly from this blog) and try to
// determine the post ID it represents.
function url_to_postid($url) {
    global $wp_rewrite;


    // First, check to see if there is a 'p=N' or 'page_id=N' to match against
    preg_match('#[?&](p|page_id)=(\d+)#', $url, $values);
    $id = intval($values[2]);
    if ( $id ) return $id;


    // Check to see if we are using rewrite rules
    $rewrite = $wp_rewrite->wp_rewrite_rules();


    // Not using rewrite rules, and 'p=N' and 'page_id=N' methods failed, so we're out of options
    if ( empty($rewrite) )
        return 0;


    // $url cleanup by Mark Jaquith
    // This fixes things like #anchors, ?query=strings, missing 'www.',
    // added 'www.', or added 'index.php/' that will mess up our WP_Query
    // and return a false negative


    // Get rid of the #anchor
    $url_split = explode('#', $url);
    $url = $url_split[0];


    // Get rid of URI ?query=string
    $url_split = explode('?', $url);
    $url = $url_split[0];


    // Add 'www.' if it is absent and should be there
    if ( false !== strpos(get_settings('home'), '://www.') && false === strpos($url, '://www.') )
        $url = str_replace('://', '://www.', $url);


    // Strip 'www.' if it is present and shouldn't be
    if ( false === strpos(get_settings('home'), '://www.') )
        $url = str_replace('://www.', '://', $url);


    // Strip 'index.php/' if we're not using path info permalinks
    // this is wrong!!!!
    //if ( false === strpos($rewrite, 'index.php/') )
    // $rewrite is an array, not a string
    // so this should work:
    if ( false === strpos(key($rewrite), 'index.php/') )
        $url = str_replace('index.php/', '', $url);


    if ( false !== strpos($url, get_settings('home')) ) {
        // Chop off http://domain.com
        $url = str_replace(get_settings('home'), '', $url);
    } else {
        // Chop off /path/to/blog
        $home_path = parse_url(get_settings('home'));
        $home_path = $home_path['path'];
        $url = str_replace($home_path, '', $url);
    }


    // Trim leading and lagging slashes
    $url = trim($url, '/');


    $request = $url;


    // Done with cleanup


    // Look for matches.
    $request_match = $request;
    foreach ($rewrite as $match => $query) {
        // If the requesting file is the anchor of the match, prepend it
        // to the path info.
        if ( (! empty($url)) && (strpos($match, $url) === 0) ) {
            $request_match = $url . '/' . $request;
        }


        if ( preg_match("!^$match!", $request_match, $matches) ) {
            // Got a match.
            // Trim the query of everything up to the '?'.
            $query = preg_replace("!^.+\?!", '', $query);


            // Substitute the substring matches into the query.
            eval("\$query = \"$query\";");
            $query = new WP_Query($query);
            if ( $query->is_single || $query->is_page )
                return $query->post->ID;
            else
                return 0;
        }
    }
    return 0;
}