This launchd script will ensure that your Docker environment on your Mac will have 10.254.254.254 as an alias on your loopback device (127.0.0.1). The command being run is ifconfig lo0 alias 10.254.254.254.
Once your machine has a well known IP address, your PHP container will then be able to connect to it, specifically XDebug can connect to it at the configured xdebug.remote_host.
Copy/Paste the following in terminal with sudo (must be root as the target directory is owned by root)...