Fix incorrect database tables being referenced on subsites in Multisite

[felixarntz]

Fixes #859

• A new Amend_DB_Base_Prefix trait is introduced to abstract away this complication in a single place.
• That trait is now used anywhere the database prefix is being altered.

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[felixarntz]

@swissspidy Any advice here on how we can avoid the PHPStan failures in https://github.com/WordPress/plugin-check/actions/runs/13018635484/job/36313903361?pr=865? It doesn't seem to recognize wpdb. But what's particularly strange to me is: Why does it fail now but didn't fail before this PR?

[swissspidy]

@swissspidy Any advice here on how we can avoid the PHPStan failures in WordPress/plugin-check/actions/runs/13018635484/job/36313903361?pr=865? It doesn't seem to recognize wpdb. But what's particularly strange to me is: Why does it fail now but didn't fail before this PR?

Good question. Maybe because this is in a trait and not a class. I'd need to check this in more detail. In the meantime I pushed a small fix.

[felixarntz]

@swissspidy Thanks! Seeing the fix, I'm thinking it would be cool if PHPStan supported this via @global annotations alone. Those already include the type, so I wonder why they are not being relied on when present.

[swissspidy]

I think the WordPress stubs/extension actually recognizes any global $wpdb variable, without any need for PHPDoc. But again, there might be something different about traits and this would need to be further investigated.