[PHP] Running functions as other than nobody

[Dav�� �rn J�hannsson]

I need to chmod files which are owned by a nother user than nobody with
a php script runing from a browser.
 
lets say i have a file called image.gif and I want to
chmod(�imgage.gif�, 0777); and I want to run it as user: myuser with
passwd: passwd.
 
Can I do this?
 
Regards, David