PHP already has functions to swap uids and guids, posix_* (see www.php.net/posix).

Derick

http://php.net/posix_setuid

Those functions are very good, except they cannot be used in a hosting context where the users are not root...

There should be a mechanism like Apache has for .cgi's (per virtual host or location) or dynamically establishing the owner via the home directory lookup.

ooops should've changed the status before...

This is part of Apache &/or the web server responsiblity, doing it in PHP, would (apart from duplicate resources), be a bit security headache..

I believe it is a feature of Apache 2. 

If you are looking at cgi's, you could consider the php-cgiwrap that is available on the net somewhere.

Its not really (AFAIK) ever going to be a php feature.

There is no official solution for this. But you might want to read my posting:

http://news.php.net/article.php?group=php.dev&article=81135

although there are some people who believe in the greater security of mod_php as mod_php has no write access to the home directories of the user. 

feel free to contact me for further questions about php-cgiwrap by private mail.

Apache 2.0's per-child mpm will have a solution for this eventually.  This can not be done at the PHP level effectively.