Like he already did a few times in the past, Composer co-creator Jordi Boggiano published some interesting statistics on PHP version usage as measured by Packagist.

A few observations: PHP 7.1 is still on top but 7.2 is closing real quick with already 1/5th of users having upgraded. That's the biggest growth rate for a newly released version since I have started collecting those stats. Ubuntu 18.04 LTS ships with 7.2 so this number will likely grow even more in the coming months.

https://seld.be/notes/php-versions-stats-2018-1-edition