From the Gartner post:

I just published a research note on PHP. Clients can find it here. The research note goes into *much* more detail but the overview is [in the rest of the post]. Keep in mind that this content is targeted at mainstream IT organizations. PHP has been a cornerstone technology on the Web for more than a decade. While its adoption among mainstream IT organizations has been limited in the past, many corporate application development (AD) projects are discovering the unique benefits of PHP.

Danne highlights two quotes that were of particular interest in the report - one from the quote above about PHP being a cornerstone of many corporate web application development and the other talking about PHP's role not just in backend application development but also it being useful in front-end toolsets too.