When did the API of apcu_cache_info() change, and how? - php

Question

We're using APCu as a data cache for PHP on a number of different installations - workstations, development and production servers. Unfortunately, the APCu API appears to be a moving target, and there is little to no official documentation (that I could find). At the moment, we're getting quite different return values for apcu_cache_info()...
With APCu 4.0.1, an entry looks like this:
[
'key' => 'the_entry_key',
'atime' => 1450646021,
'ctime' => 1450646021,
'mtime' => 1450650861,
'dtime' => 0,
// ...
]
With APCu 4.0.7, it looks like this:
[
'info' => 'the_entry_key',
'access_time' => 1450650861,
'creation_time' => 1450646021,
'modification_time' => 1450646021,
'deletion_time' => 0,
// ...
]
According to the source on GitHub, it now looks like this:
[
'info' => 'the_entry_key',
'access_time' => 1450650861,
'creation_time' => 1450646021,
'mtime' => 1450646021,
'deletion_time' => 0,
// ...
]
We've seen other sudden API changes in the past, like when apcu_sma_info() and apcu_cache_info() had to be called with the string "user" as the first parameter - until they didn't. I understand that these changes are related in some way with keeping or dropping compatibility with the old APC extension, but it's getting a little hard to guess how to interact with APCu.
Are these changes documented somewhere, with a version number we can check against? Are there going to be any more changes to this in the near future? How can I get notified about them, other than seeing my application break?
The documentation on php.net has nothing to say about this, and neither does the project's CHANGELOG file. The PHP change log doesn't mention this as a backwards incompatible change either (probably because APCu isn't bundled with PHP by default).