chown on a file/folder

[pollux0]

i am building a web based app which will adminstrate my imap/smtp server. using php I need to be able to change the owner on a folder. i am using this command and getting errors:
chown("/usr/local/virtual/username", "testUser"

from what i have read this can only be done by a superuser such as root because the user/password files need to be read in /etc

can anyone suggest another way to do this? mabey execute a script on the server?

thanks in advance