$sites global (containing all networks) no longer exists, with no replacement

[rmccue]

#27003 removed the $sites global containing an array of networks on the installation. This broke the switch_to_network functionality of ​WP Multi Network, as it expected this variable to be set.

Given that we've gone almost a whole release without anyone missing it, I think it's fine to leave it gone forever. That said, there appears to be no replacement to get all networks.

We should add a wp_get_networks, and it should also cache this result. wp_get_network could then be adapted to take advantage of this cache if it exists.

Related: #29411

[rmccue]

Also note, nacin on #27003:

I figure that wp_get_network() will eventually start returning a proper object, so I wanted to go ahead with this abstraction now. Also, originally, there was some decoration that occurred in wp_get_network(). It doesn't matter for the moment. That said, emphasizing that a DB row should be passed through to wp_get_network() sets a good standard for others to do so, which means the migration to a proper object might be smoother.

With this, we might want to look at actually making those objects.

[ethitter]

29415.patch​ is a basic start for wp_get_networks().

The function supports basic arguments--domain, path, limit, and offset--for which networks are to be retrieved. Like wp_get_sites(), the results from $wpdb are returned directly as an associative array.

I consciously left caching out of this first pass; I'm not sure how beneficial it will be. On an instance with only a few networks, the cache lookup may not be any faster than the DB lookup. On a large network where there may be a benefit, storing all networks in a single array could encounter issues with cache value sizes.

This needs tests as well, but I'm looking first for feedback on arguments and the need for caching. Without any use cases in Core currently, it's hard to anticipate deficiencies in my initial approach.

[wonderboymusic]

I am assuming this needs a refresh

[jeremyfelt]

We should probably do this hand in hand with WP_Network_Query in #32504.

[jeremyfelt]

Pushing this back to Future Release until we have better groundwork.

[jeremyfelt]

I forgot about this ticket while we were working on #32504. Now that get_networks() is available, we should be able to consider this closed.

Thoughts?

[jeremyfelt]

Considering this fixed via [37895].