error handling in php request adapter

[baywet]

The changes added by #1100 to address #411 should be implemented in PHP generation, abstraction and http as well.
In the pull request you'll find a set of checklist per language that should help understand the required changes.
You'll also find the changes for the other languages as well as some documentation changes.
Don't hesitate to comment here if this is not enough material and if you have additional questions.