How to save posts as a text file

Question

I am developing a mobile Application that users can view their Blog posts and also make posts to their blogs via a mobile phone. I also want it in such a way that the users can save a particular post of interest for future references or to read when they are offline. What I intend doing is to save the post as a text file and save the title, Author, Date-Published and category in the database. I should also keep record of the number of entries such that it prompts one to delete an item if the number of saved items is up to 5. Please can someone help me with how to go about saving.