Jordi Boggiano has a new post today sharing some of his own insights about PHP version adoption but, unlike some of the raw numbers shared before, his perspective comes from aggregating data from Packagist.
Pascal's number are interesting but I believe they have a bias towards older PHP versions. I would argue that people configuring their servers properly are also those that tend to keep up to date with newer versions, and part of the best practices is to avoid publishing the software versions you are using (i.e. disable expose_php in php.ini). If I am correct here that means early adopters are mis-represented in those numbers. In any case, I do have another biased dataset to present so here it comes! I looked in the packagist.org logs of the last fifty days for GET /packages.json which represents a composer update done by someone.
He notes that the data is biased towards development machines (not always running the same version as their production counterparts) but that it shouldn't skew the numbers too much. He compares two different datasets, one from November 2013 and the other from November 2014, showing a major change in the overall numbers and moving the largest version used up from 5.3.10 to 5.5.9. He also shares some interesting statistics around the requirements developers are putting on Packagist packages...that have basically remained the same over the past year (sadly).