I read your project brief and can add the functionality you want. I can modify your script to use the database for storing visited links along with visit counts. It will only show you those articles at random which has a minimum number of visit count after it won't find any new articles in your feed.
Relevant Skills and Experience
I'm a Web Developer having experience in HTML5, CSS3, JavaScript, PHP, MySQL, and XML. You can count on me for your project.
Feel free to discuss your project with me so I can better assist you.
Proposed Milestones
$50 USD - Project Completion