This predates php7.2 and Docker-based Jenkins jobs and seems unused, time to remove?
We might still have some old legacy jobs that could still be relying on the php wrapper (the migration was/is tracked by Continuous-Integration-Infrastructure (Slipway)). It is in integration/jenkins.git in bin/php.
Maybe we can make the wrapper to log some information whenever it is being used? I guess a log file or some spam mail might work.