Bug with changing the language in the "General settings".

[daniluk4000]

If we change the language (in the example, English to Russian) notification will be on the old language. I think this is a bug, otherwise, correct me.

[daniluk4000]

If we change the language in General Settings*

[ocean90]

This is currently fixed in my patch for #15677.

[ocean90]

In 29630:

Language packs: No WPLANG anymore.

• The WPLANG constant is no longer needed. Remove define('WPLANG', ); from wp-config-sample.php. Populate WPLANG option based on the WPLANG constant. When get_option('WPLANG') is an empty string it will override WPLANG.
• Introduce translations_api() which is available to communicate with the translation API. Move translation install related functions to a new file.
• Replace mu_dropdown_languages() with wp_dropdown_languages(). wp_dropdown_languages() is now populated by the translation API.
• Remove wp_install_load_language() and allow load_default_textdomain() to switch a core translation.

fixes #13069, #15677, #19760, #28730, #29281.

[ocean90]

In 39122:

I18N: Show "Settings saved." in the correct language after switching the site language.

This simplifies the logic by comparing get_user_locale() before and after an settings update.

Props swissspidy, ocean90.
See #29783, #29281.
Fixes #38482.