#1 it wouldnt be my preference
#2 it probably wouldnt be considered a sitemap by google
#3 it should still expose the content
sitemaps generally should be xml or txt files according to the official guidelines. we know that google follows links that it finds online. you could just add all the links to a html or php file and then publish that file online. it should serve the purpose of exposing your content but will not enjoy the full benefits that the official sitemaps are given.