chown() changes the ownership of the specified file. Since this function on nearly all UNIX systems is restricted to being run by the superuser, it won't operate correctly when PHP is run as a module (unless you run httpd as root). This function always returns TRUE on Win32 platforms.
If safe mode is enabled, chown() can only change the ownership of files that are owned by the user running the command. In most cases, this is the user that the web server runs as.
PHP Functions Essential Reference. Copyright © 2002 by New Riders Publishing (Authors: Zak Greant, Graeme Merrall, Torben Wilson, Brett Michlitsch). This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/). The authors of this book have elected not to choose any options under the OPL. This online book was obtained from http://www.fooassociates.com/phpfer/ and is designed to provide information about the PHP programming language, focusing on PHP version 4.0.4 for the most part. The information is provided on an as-is basis, and no warranty or fitness is implied. All persons and entities shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from the information contained in this book.