I am considering to move frome Microsoft languages to PHP (just for web dev) which has quite an interesting syntax, a perlish look (but a wider programmer base) and it allows me to reuse the web without reinventing it. I have some concerns too. I would be more than happy to gather some wisdom from stackoverflow community, (challenge to my opinions warmly welcome). Here are my doubts.

1. Efficiency. Cgi are slow, what I am supposed to use? Fastcgi? Or what else?
2. Efficiency + stability. Is PHP on windows really stable and a good choice in terms of performances?
3. Database. I use very often MSSQL (I regret, i like it). Could I widely and efficiently interface PHP with MSSQL (using smartly stored pro, for example).
4. XSLT + XML performance. I work quite a lot with XML and XSLT and I really find the MS xml parser a great software component. Are parser used in PHP fast, reliable and efficient (I am interested mainly in DOM, not SAX)?
5. Objects. Is the PHP object programming model valid end efficient? 6 Regex. How efficient is PHP processing regexp?

Many thanks for your advices.