My recent experience is PHP eats more memory. But it matters when you are running it under memory constraint device. For a high end server its not a matter. I built an chat server using socket functions which was intended to run on embedded device. I didn't want to load apache. So I wrote it in plain PHP (as I am good at it). The server was working good until I my memory runs out. My memory requirement was really low, about 32M. Thats the total memory for everything. I ran a heavy RIA chat application with. Later I change the language to non-PHP (name of that language might start flame-war). Now its working well so far.
One thing I know is, If you want to do it, you can do it. It'll need some effort but still doable. Performance optimization comes after development. So you can have your high performance enterprise application server. -- Shiplu.Mokadd.im ImgSign.com | A dynamic signature machine Innovation distinguishes between follower and leader