Run IIS and Apache on same server

There is no problem of runing php via IIs, its a very normal that php will run under IIS

anyway, if you want to run 2 webserver (IIs and apache) then you will have to define different port number for One webserver

you cant run both IIs and apache on port 80

so if your IIS run on port 80 , then you will have set apache to run on port 8080 ( or other)

and you will have to call any website running on apache like this

www.mydomain.com:8080

I would run PHP on IIS but I need to make use of Apache specific features like .htaccess for URL rewriting.

Also, can you not just run each IIS and Apache on a different IP?

YOu can have more then 2 ip , its fine.
but when some one will type www.mydomain.com

all trafiq will come to your server via port 80.

so by default IIS and apache will try to run on port 80, and 2 services cant run on Same port, so you will have to change port number for one webserver.

so if www.mydomain.com run under IIS -> 80  it wil come straight forward
now if www.acbc.com run Under apache -> 8080  -. you will have to say which port to go.

have read this one , about IIS support url rewrite , it would not be perfect like httacces but you can have a look

http://ask-leo.com/does_iis_support_url_rewriting.html