In this example, the `chmod()` function is used to set the permissions of the file to 664, which grants read and write access to the file owner, the group, and all other users on the system. This code assumes that the user running the PHP script is part of the group that needs write access to the file. The package library used in this example is the core PHP file manipulation functions, which are part of the standard PHP library and do not require any additional packages or libraries to be installed.