RSS Feed Checker

The RSS Feed checker looks through your blogroll for links with rss feeds and then stores the name and url of the latest article.
The Links RSS Enhanced widget then displays the latest links in descending order.
The idea for the widget comes from the blogroll widget on blogger.

Version 2.0 for PHP 8 and above only. Only tested on 6.9.
For earlier versions of PHP use Version 1.1

Technical section

The plugin will create an extra table in your wordpress database to store the latest feed updates,
this will be called links_rss with the prefix for your database e.g. wp_links_rss

A Cron (schedule) is created to run every 30 minutes and process links. Note that Cron in WordPress
depends on hits, your WordPress website receives. So playing with this plugin within an offline
environment (MAMP, XAMPP, WAMP etc.) without anyone or anything triggering the scheduling by
sending requests to the WordPress page won’t produce any results if you do not trigger it by
yourself.

References

A selection of places I’ve found help for this plugin.

Thanks also to Ozh, Roland Rust and for their explainations and examples

Admin UI

• https://codex.wordpress.org/Function_Reference/add_meta_box
• https://codex.wordpress.org/Administration_Menus#Page_Hook_Suffix
• http://wpengineer.com/1295/meta-links-for-wordpress-plugins/
• http://www.code-styling.de/english/how-to-use-wordpress-metaboxes-at-own-plugins
• http://planetozh.com/blog/2008/02/wordpress-snippet-add_meta_box/
• http://wptheming.com/2011/08/admin-notices-in-wordpress/
• http://www.prelovac.com/vladimir/improving-security-in-wordpress-plugins-using-nonces

Ajax

• http://return-true.com/2010/01/using-ajax-in-your-wordpress-theme-admin/
• http://amiworks.co.in/talk/simplified-ajax-for-wordpress-plugin-developers-using-jquery/
• http://xplus3.net/2008/10/16/jquery-and-ajax-in-wordpress-plugins-administration-pages/
• http://www.garyc40.com/2010/03/5-tips-for-using-ajax-in-wordpress/

Database

• http://createmy.com.au/connecting-your-plugin-to-the-wordpress-database/
• http://webjawns.com/2009/08/the-wordpress-wpdb-class-explained/

Scheduling

• http://wpseek.com/source/wp/latest/nav.html?wp-includes/cron.php.html
• Ideas on background processing from the broken link checker

Settings

• https://codex.wordpress.org/Settings_API – new way to handle options/settings
• http://ottopress.com/2009/wordpress-settings-api-tutorial/
• http://planetozh.com/blog/2009/05/handling-plugins-options-in-wordpress-28-with-register_setting/
• http://wpengineer.com/2139/adding-settings-to-an-existing-page-using-the-settings-api/
• http://blog.gneu.org/2010/09/intro-to-the-wordpress-settings-api/
• http://alisothegeek.com/2011/01/wordpress-settings-api-tutorial-1/

RSS Feeds

• http://jaewon.mine.nu/jaewon/2010/10/30/how-to-make-your-wordpress-a-rss-reader/
• https://codex.wordpress.org/Plugin_API/Filter_Reference/wp_feed_cache_transient_lifetime
• http://simplepie.org/