Teach yourself PHP

https://www.geeksforgeeks.org/php/

Developing custom sections in PHP

https://www.lianja.com/doc/index.php...ections_in_PHP

Developing custom gadgets in PHP

https://www.lianja.com/doc/index.php...Gadgets_in_PHP

Understanding UI layouts

https://www.lianja.com/doc/index.php...ing_UI_Layouts

Understanding Custom delegates

https://www.lianja.com/doc/index.php...stom_Delegates