Android has full native support of RTL layout or text orientation since SDK 17 (Jelly Bean). Mostly mobile apps are designed in LTR (Left to Right) but few languages/designed are written from RTL (Right to Left).
PHP session is used to store information in a variable temporarily to be used across multiple pages. PHP session creates unique user id for each browser to recognize the user and avoid conflict between multiple browsers.
PHP is one of the most popular open-source and server-side scripting language. PHP is a powerful tool for making dynamic, interactive websites and you can do much more with it. It can be learned easily.