[code snippet] live-replace URLs before serving page

I wrote a dirty code snippet to live-replace URLs in content before a page is served. I’m posting it here because I want everyone to take shots at it and help this become a snippet that works for all situations. Obviously, the best thing would be to actually find/replace strings in the database, however this opens us up to corruption risk and other time-consuming cleanup if it screws up.

This lets the Redirection plugin continue handling uncaught (i.e. external) redirects AND live-fixes things at render-time (which is horrible if you’re not caching, but then again, what kind of animal are you if you’re not caching to some degree? LOL)

function replace_old_links_in_content($content) {

    // Ensure Redirection plugin is active; if not, BAIL EARLY
    if (!is_plugin_active('redirection/redirection.php')) {
        return $content;
    }

    // FOR DEBUGGING, if you need it:
        // Define allowed post types and specific post IDs (set to null to apply to all)
        $allowed_cpts = []; // Change to post types you want; [] = all/any; ['post'] = only posts
        $allowed_post_id = []; // Change to specific post IDs for testing; [] = all/any; [1,2] = only post ID 1 and 2
    // END DEBUGGING

    // Get the current post object
    global $post;
    if (!$post) {
        return $content;
    }

    // Check if the current post matches the CPTs or the allowed post ID
    if (!empty($allowed_cpts) && !in_array($post->post_type, $allowed_cpts)) {
        return $content;
    }
    if (!empty($allowed_post_ids) && !in_array($post->ID, (array) $allowed_post_ids)) {
        return $content;
    }

    // @TODO I know I shouldn't do this so teach me the right way for this plugin
    global $wpdb;
    $redirects = $wpdb->get_results("SELECT url as source, action_data as target FROM {$wpdb->prefix}redirection_items WHERE action_type='url' and match_type='url'");

    if ($redirects) {
        foreach ($redirects as $redirect) {
            // @TODO this all needs to be rewritten to take all the pattern matching into consideration (or use the API). I told you this is a dirty snippet.
            // 
            $old_path = trim($redirect->source, "/"); // Remove leading/trailing slashes
            $new_url = esc_url($redirect->target);

            // Generate the full site URL dynamically
            $site_url = home_url("/{$old_path}/");

            // Create regex to match all possible variations of the old URL
            $pattern = '~https?://(www\.)?' . preg_quote(parse_url($site_url, PHP_URL_HOST) . parse_url($site_url, PHP_URL_PATH), '~') . '?(/)?~i';

            // Perform regex replacement
            $content = preg_replace($pattern, $new_url, $content);

        }
    }

    return $content;
}

add_filter('the_content', 'replace_old_links_in_content', 20);

Implementation:

• do not use on a production site
• try it using the Code Snippets plugin:
• create a new snippet, copy/paste this into the snippet with title INFRASTRUCTURE | LIVE-fix old URLs based on Redirection plugin rules , set it to run on front-end only, Save+Activate
• go to some pages that used to have old URLs – they should now be rewritten to the new/correct URLs

Known Flaws:

• Shouldn’t directly access the database – I want help with this
• Needs a more careful, less greedy approach to matching i.e. within links only
• Needs to work also for relative URLs
• If redirection is being used to create short links and these are used in posts/pages, they’re all gonna get replaced and you’ll lose tracking (if that’s how you’re using Redirection)
• Probably many more. As I said, this is a dirty snippet.

• This topic was modified 2 weeks, 3 days ago by James Revillini. Reason: providing implementation notes and some more detail on flaws