> I'm just interested in pivot points where companies decided to switch from technology x to technology z, and what made them do it.

There's a lot of articles and blog posts on that topic, enough to keep you occupied for a long while. Here's one:

http://www.smashcompany.com/technology/my-final-post-regardi...

Here's another

https://blog.asana.com/2017/08/performance-asana-app-rewrite...

> I meant, "When did people stop deciding to greenlight new projects using PHP?"

Did they, though? I haven't noticed. Do you have any source on that?

> Would you be interested in such a chart?

No.