Ensure post abstraction methods use correct site ID.

[peterwilsoncc]

Description of the Change

This resolves an issue in which the post abstraction can return a mix of data on Multisite networks when the site is switched.

It introduces the DistributorPost::__call() magic method to ensure the current site (get_current_blog_id()) matches the site ID used to instantiate the object.

To match the PHP behavior without the magic method, a fatal error is thrown if the method name does not exist.

To discourage developers from calling the helper methods while using a switched site, a notice is thrown if the magic method needs to switch sites.

To avoid site switching when possible, an in memory cache is used to bypass the site switch the second or subsequent time a method is called. The cached data is only used if the object is called from the wrong site to reduce the risk of errors caused by the addition/removal of hooks during runtime. Basically it's a performance compromise.

Closes #1007.
Supersedes #1004.

TODO

• Test interaction of magic methods: ensure $dt_post->source_site doesn't result in multiple switches

How to test the Change

Changelog Entry

Fixed - Inconsistent data returned from post abstraction after site switch on multisite.

Credits

Props @peterwilsoncc, @dkotter

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[peterwilsoncc]

::__get() and ::__isset() methods are unchanged but have been relocated to group all the magic methods together.

[peterwilsoncc]

In the revised PR #1010 (in draft), I went with a __call magic method to avoid statics. I'll see if I can use a cache to avoid switching sites when the method is used a second time.

[peterwilsoncc]

Mini plugin I've been using for testing and checking error logs