Tool/library to determine minimum PHP version to run a script

[ggiunta]

Does a similar tool / php script exists?

It should not be difficult to develop, once you've got a working PHP parser:
just make a table of all used functions and constants and check out for every one the minimum version of the PHP interpreter that supports it.

It couldd even give some hints on needed extensions/php.ini options...

Thanks, gGaetano