how to build a controller that creates an xml sitemap?

[aZoTGwFg]

I know this question may seem confusing and/or a duplicate question. I have searched previous questions but couldnt find one that fits my case.I am using Codeigniter. My boss has asked me to build a controller (or if possible an application in php) that autogenerates a sitemap.xml for the site. Sitemap should follow this structure:\[code\]<url> <loc></loc> <changefreq></changefreq></url>\[/code\]It should also include information that's not on the web, but on the database. I'm confused about this, because for what I know sitemaps are based on links from the site. (Then again, I know nothing about xml so that's a reason for all my confusion). For example, one part of the site has a 'newsfeed', this shows the latest 5 news from the database. What my boss wants is for old news to be indexed as well.I should point out that the site uses two different databases. One for the news on the newsfeed, and another for the rest of products in the site. (Each product has its own link, some products are not on site only on database, and my boss wants those products on sitemap either way). Any ideas on how to do this would be greatly appreciated, since I have no clue on where to start. Thanks for your time