First I would like to say that I have had PHP experience but not enough to
say I am a PHP developer.

I want to use PHP to build a site that uses MySQL, I am building it from
scratch so I don't know where to start, should I start with PHP and design a
database around my code, or should I designs the db and design the site are
the db.

is it just a matter of preference or is there a recommended way to do this?

Thanks