what is php used for

PHP can generate dynamic page content.
PHP can create, open, read, write, delete, and close files on the server.
PHP can collect form data.
PHP can send and receive cookies.
PHP can add, delete, modify data in your database.
PHP can be used to control user-access.
PHP can encrypt data and apply validation.
PHP used to send and receive E-Mails.
PHP can be used to integrate with other third party tools.
PHP can output images, PDF files, and even Flash movies. You can also output any text, such as XHTML and XML.
  

Lua is a powerful and fast programming language that is easy to 
learn and use and to embed into your application. 

Lua is designed to be a lightweight embeddable scripting language.
It is used for all sorts of applications, 
from games to web applications and image processing.

-- 

Used commonly in Roblox, Garry's Mod and Multi Theft Auto

C# was developed by Microsoft and is used in essentially all of their products. It is mainly used for developing desktop applications and, more recently, Windows 8/10 applications. It is also a part of . NET so it is used alongside languages like ASP in web development and apps.

%d is used to specify an integer, %u is used to specify an unsigned integer .

PHP is a scripting language normally used by web developers to build websites.
It supports object oriented programming.
It even has support for building windows desktop applications with PHP Desktop

PHP is a server side scripting language. that is used to develop Static websites or Dynamic websites or Web applications. PHP stands for Hypertext Pre-processor, that earlier stood for Personal Home Pages. PHP scripts can only be interpreted on a server that has PHP installed.