Uploading files in a webapp can be extremely tricky and sometimes the quickest way to do it is to store the file directly in the webserver or into a DNS (like Amazon S3) and then to save the link and the metadata inside a table in the DB. The thing is that you'll have to deal with file permissions, server storage, file management and so on (which is perfectly fine, by the way).
This article is helpful only if you have the following situation:
A web app which uses facebook login to login its users and if a user is logged out from his/her facebook account through another browser tab, then your app dont know that he is logged out out or not from his facebook account and he/she will remain as logged in your web application.Its ok if you have no problem with this situation.But if you want to forcefully logout the user from your application if he is logged out from his facebook account means you can try this example.This example uses periodic ajax calls to facebook's graph api to check whether the user is logged in or not.
So I've been busy making lots of modifications to my views/models/controllers - came to test the app and got a blank screen. Nothing in the application.log file so must be a syntax error somewhere... But which file?
The article Fixing extensions without modifying their code reminded me of another patching technique that I used. My conviction and a hard look on the web had led me to an article Redefine PHP class methods or class giving me a head start to do what I wanted: patching third party code without touching the original to allow easy upgrades.