i m a professional website designer and interested in learn PHP for Future
so can any one explain me where PHP required in website during development or design
and what is the main topic which most required for Website Designer or developer

I have knowledge about programing like c,c++ ,java or script so don't want to waste my time on basic
of programing structure. i just want to learn main topic that ever required in website
front hand or backhand both
explain me complete modules and topics