CodeIgniter is a free, open-source, easy-to-use, object-oriented PHP web
application framework, providing a ready-to-use library to use with
your own PHP applications. For example, there is a Database API to make
it easier and more convenient to execute SQL queries, such as SELECT,
UPDATE, DELETE, INSERT, etc., without having to create a lot of
repetitive code yourself. This is how an application framework is useful
in application development.