I'm not sure how php would be 'down', the web server may be down or php may be incorrectly installed. I may be wrong, but my understanding is that once correctly installed php is available when the web server is available, unless someone has been playing with httpd.conf or php.ini
In Sangre's case, where his browser didn't recognise the php extension, all he would download would be the html part of the script.
Blu