This is a proposed feature for Composer in which you would be able to add a --global
option to manipulate installed packages at a system-wide / user-wide level.
This should not be used for autoloading, but rather just for running any binaries.
Some projects provide utilities to be run via the command line. Like other package managers, these packages should be able to be installed at a global level so the commands can be run as long as you have the bin directory in your PATH.