Plugin to automatically change anchor text of urls to the destinations title?

Decided to entertain the idea. Adapted from my snippet that changes anchors to collapsed domain names. Little too verbose, but seems to work.

add_filter( 'the_content', 'anchors_to_page_titles' );

function anchors_to_page_titles( $content ) {

    preg_match_all( '/<a.*?href="https://wordpress.stackexchange.com/questions/6023/(.*?)".*?>(.*?)<\/a>/', $content, $matches );
    array_shift( $matches );

    foreach( $matches[0] as $key => $url ) {

    $anchor = $matches[1][$key];

    if( $url == $anchor ) {

        $transient_key = 'page_title_'.md5($url);
        $anchor = get_transient($transient_key);

        if( !$anchor ) {

            $response = wp_remote_request($url);
            $body = wp_remote_retrieve_body($response);
            $pattern = '/title>(.*?)</';
            $title = array();
            preg_match( $pattern, $body, $title);

            if( !empty( $title ) ) {

                $title = $title[1];
                $anchor = $title;
                set_transient( $transient_key, $anchor, 60*60*24 );
            }
            else {
                $anchor = $url;
                set_transient( $transient_key, $anchor, 60*60 );
            }
        }

        $content = str_replace( ">{$url}</a>", ">{$anchor}</a>", $content );
    }

    }

    return $content;
}

PS maybe it would make sense to modify post on save rather than filtering on display… Well, as per my comment I don’t think page titles are good for this anyway.