I'm about to start learning PHP, for which I'll need

Apache Server
some db: mySQL
a PHP compiler (<--- is this correct?)

1. At present, I have PWS installed on my machine, and I work with ASP. Will there be a problem if I get Apache? If so, what should I do about it?

2. Do I need a PHP compiler, or will Apache do the compiling for me?

3. Are there any PHP editors out there? Like there is Visual InterDev for ASP.

Thanks.