How do you keep track of PHP versions across client sites?

PHP2Shell had us checking which PHP build every client server was actually running, and it took far longer than it should have. Checking php -v isn't enough, distro packages keep the old version number, and some sites sit behind managed hosts.

If you look after lots of client sites, how do you handle it? A spreadsheet, Forge, a monitoring tool, or a script you've written?

(We've been building something for this, Porro, launching here on Tuesday. But I'm genuinely curious how other agencies do it.)