command_map for piped commands

Given:
The SSHKit (capistrano) command in question is:
`execute :curl, "-s", fetch(:composer_download_url), "|", :php`

My PHP binary is in the following path and set so:
`SSHKit.config.command_map[:php] = '/usr/local/bin/php54'`

Problem:
The `:curl` symbol is correctly replaced from the command map, but the `:php` symbol is not.

I've tested replacement by changing the `:curl` value in the command_map and succeeded, so I'm guessing it's because `:php` is in a pipe or is the second substitution that it is not replaced?