Explicitly globalize global variables in ms-settings.php

[danielbachhuber]

ms-settings.php uses and sets a few implicitly global variables:

• $domain
• $path
• $blog_id
• $site_id
• $public
• $table_prefix

It would be more correct if these were explicitly globalized in the file header.

Discovered in ​https://github.com/wp-cli/wp-cli/pull/3695

[johnjamesjacoby]

Agree. We should definitely do this, and it should lead us down the path of education & awareness around their existence and what their intended purposes are.

Multisite has more than a few dedicated globals, and several of them are very situational (sign-ups, site creation, etc...) so I'm sure they've probably created several hours of work for people who needed to discover them the hard way.

[jeremyfelt]

Yeah, I'm on board with explicit.

• $blog_id is declared in wp-settings.php as of [34961], so that should be okay already.
• I noted previously that $site_id and $public are no longer used anywhere by core. It'd be great if we could just null these out, but who knows what would break. Note that we kind of accidentally did this with $sites and it only came up once. See #29415.
• $path is used in validate_another_blog_signup(), probably by other plugins, etc..
• $domain is used in wpmu_validate_blog_signup(), and possibly elsewhere.
• $table_prefix is at least used a few times (object cache drop-ins, wp_set_wpdb_vars()). It's first used in wp-settings.php, so should be defined there as well.

[csloisel]

May need phpdoc descriptions

[DrewAPicture]

Assigning ownership to mark the good-first-bug as "claimed".

[stevenkword]

39419.diff​ applies cleanly against trunk as of July 10, 2017.

PHPdoc descriptions are missing.

@csloisel -- Do you intend on updating the doc to get this one ready for committer's eyes? Do you need any help or have any questions?

[earnjam]

Created #41285 to have further discussions about removal of $site_id and $public

[jeremyfelt]

It looks like we can do a bit more with the patch. A couple notes:

• We'll need documentation next to each global that describes its purpose.
• $table_prefix should be documented in wp-settings.php instead of ms-settings.php.
• We can remove $site_id and $public. See #41285.

@csloisel - if you are interested, please feel free to update the ticket with a new patch. I'm going to reassign the ticket to you.

[jeremyfelt]

I started taking a stab at the docs for these in 39419.2.diff​. I added Deprecated next to $domain, $path, $site_id, and $public to try and indicate that they should not be relied on. I'm not sure if there's a better way to do that.

$table_prefix is interesting because it's first used in wp-config.php. We can probably still document it in wp-settings.php though.

[johnjamesjacoby]

39419.2.diff looks OK to me.

I agree with @jeremyfelt's original assessment of $blog_id and $table_prefix`.

[jeremyfelt]

39419.3.diff​ adds usage suggestions for "deprecated" globals.

[jeremyfelt]

$table_prefix is already explicitly globalized in wp-settings.php, see [18993]. I'm going to go with 39419.3.diff​ for 4.9.

[jeremyfelt]

In 41875:

Multisite: Explicitly globalize global variables in ms-settings.php.

Explicitly globalize and document $domain, $path, $site_id, and $public in `ms-settings.php.

Props csloisel, danielbachhuber.
Fixes #39419.