Jeff Geerling shares the best way to get the full PHP version string. I’d think that “php –version” externally or “echo PHP_VERSION” internally would do the job. However, that’s not exactly right, as there are a number of inconsistencies on different platforms. The best option seems to be the combination of the PHP_MAJOR_VERSION, PHP_MINOR_VERSION, and PHP_RELEASE_VERSION constants.
$ php -r 'echo join(".",[PHP_MAJOR_VERSION,PHP_MINOR_VERSION,PHP_RELEASE_VERSION]);'
7.2.12