i.e to replace Apache with a PHP application that sent back html files when http requests for .php files are sent?
How practical is this?
Just FYI, PHP 5.4 just released with in-built webserver. Now you can run a local server with very simple commands like -
$ cd ~/public_html
$ php -S localhost:8000
And you'll see the requests and responses like this -
PHP 5.4.0 Development Server started at Thu Jul 21 10:43:28 2011
Listening on localhost:8000
Document root is /home/me/public_html
Press Ctrl-C to quit.
[Thu Jul 21 10:48:48 2011] ::1:39144 GET /favicon.ico - Request read
[Thu Jul 21 10:48:50 2011] ::1:39146 GET / - Request read
[Thu Jul 21 10:48:50 2011] ::1:39147 GET /favicon.ico - Request read
[Thu Jul 21 10:48:52 2011] ::1:39148 GET /myscript.html - Request read
[Thu Jul 21 10:48:52 2011] ::1:39149 GET /favicon.ico - Request read
It's already been done but if you want to know how practical it is, then i suggest you install and test with Apache bench to see the results:
http://nanoweb.si.kz/
Edit, A benchmark from the site:
Server Software: aEGiS_nanoweb/2.0.1-dev
Server Hostname: si.kz
Server Port: 80
Document Path: /six.gif
Document Length: 28352 bytes
Concurrency Level: 20
Time taken for tests: 3.123 seconds
Complete requests: 500
Failed requests: 0
Broken pipe errors: 0
Keep-Alive requests: 497
Total transferred: 14496686 bytes
HTML transferred: 14337322 bytes
Requests per second: 160.10 [#/sec] (mean)
Time per request: 124.92 [ms] (mean)
Time per request: 6.25 [ms] (mean, across all concurrent requests)
Transfer rate: 4641.91 [Kbytes/sec] received
Connnection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 1.9 0 13
Processing: 18 100 276.4 40 2739
Waiting: 1 97 276.9 39 2739
Total: 18 100 277.8 40 2750
Percentage of the requests served within a certain time (ms)
50% 40
66% 49
75% 59
80% 69
90% 146
95% 245
98% 449
99% 1915
100% 2750 (last request)
Apart from Nanoweb, there is also a standard PEAR component to build standalone applications with a built-in webserver:
http://pear.php.net/package/HTTP_Server
Likewise the upcoming PHP 5.4 release is likely to include an internal mini webserver which facilitates simple file serving. https://wiki.php.net/rfc/builtinwebserver
php -S localhost:8000
Why reinvent the wheel? Apache or any other web server has had a lot of work put into it by a lot of skilled people to be stable and to do everything you wanted it to do.