PHP chmod（）：不允许操作，涉及safe_mode弃用？

Question

I'm struggling a bit to grasp the concept of chmod() from PHP as the course I'm currently taking is a bit outdated and involves safe_mode. It states that as safe_mode is turned off, the restrictions to modify permissions with chmod() to a file when the owner is not the same as the one executing the command are removed. I'm working with PHP 5.5.9 in conjuncture with XAMPP, I've verified that the flags are turned off (just in case), but can't seem to get it working. As I execute the following PHP script:

echo "File permissions :" .  decoct(fileperms("file_permissions.php"));
chmod("file_permissions.php" ,0777);

I receive the following output :

Warning: chmod(): Operation not permitted

My permissions for the file are the following

-rwxrwxrwx@  1 joelhernandez  staff     24 Apr 14 06:59 file_permissions.php

And I've executed ps aux | grep httpd to confirm that the my webserver is operating under the user "daemon" .

As I change the file ownership to daemon:

-rwxrwxrwx@  1 daemon  staff     24 Apr 14 06:59 file_permissions.php

Everything works, I do not understand why as I had understood that with safe_mode turned off, file ownership would mean nothing, instead file permissions were the way to handle access.

Answer 1

The daemon user is not root, so it is not allowed to change the mode of a file owned by a different user. PHP safe_mode is not the cause here. The warning is telling you that the attempted operation failed because the web server user did not have permission to make the mode change.

The operation succeeded after you manually changed the ownership of the file to daemon because users are allowed to change the mode of files they own.