Jordi Boggiano has posted some updated statistics around the use of the Packagist site around PHP version requirements and the relation of package downloads to PHP versions.
Last year I posted stats about PHP versions, and the year before as well, both time in November. However this year I can't wait for November as I am curious to explore the PHP7 uptake!
A quick note on methodology, because all these stats are imperfect as they just sample some subset of the PHP user base. I look in the packagist.org logs of the last 28 days for Composer installs done by someone. Composer sends the PHP version it is running with in its User-Agent header, so I can use that to see which PHP versions people are using Composer with.
He compares the previous statistics against the ones gathered back in November 2015, both in numbers and graphs. He shows the stats for the PHP versions being used and for the PHP versions that are required. It's interesting to see that there's been a good uptick in supported versions including PHP 7.0+.