Unicode: LC 7.0 - PHP - MySQL?

[Tiemo Hollmann TB]

Hello,

I have a LC 6 program communicating through PHP with a MySQL db. Because my
background about Unicode, PHP and MySQL is limited I wonder what I have to
care about, when migrating to LC 7.

I have read the release notes of LC 7. My limited thinking was, that UniCode
really has a unique code for each sign on the planet. But why is there a
UTF-8 / UTF-16. Which one is LC using? Which one is my MySQL db using? I
don't find any information about UTF-8/16 in my db description. How is the
collation of the db related to UTF-x and to LC?. My tables are collated in
ascii_general_ci. In some of my PHPs a "COLLATE latin1_swedish_ci" is used.
I have no idea why this Swedish collation is in my german PHP and how it can
be compatible with my ascii_general_ci DB. (The PHPs are made by third
party)

What do I have to change in my LC program when migrating to 7. Where to
start? 

Is LCs Unicode really the magic thing, where I don't have to care about any
charset related thing and all my thinking is just waste? Or do I have to
migrate, test and dig into one crash after the other? Or do you have any
helpful hints, how to start such a migration and what to look for?

Thanks

Tiemo