Transform internationalized plugin into internationalized mu-plugin?

Question

I developed a custom plugin with the following structure in my folders:

wp-content
--- plugins
------ my-plugin
--------- languages
------------ po and mo files
--------- my-plugin.php

I internationalized it, and the translations all worked successfully. Now, I need that plugin to be a must-use plugin, by using the following structure:

wp-content
--- mu-plugins
------ my-plugin
--------- languages
------------ po and mo files
------ my-plugin.php

(The main plugin file has to be placed directly into the mu-plugins directory to be executed, from what I learned).

I now corrected all the paths in my main plugin file, due to the slight change of the location of the main plugin file (not inside the my-plugin folder anymore, but inside the wp-content/mu-plugins folder, as explained above), and all my functionalities are working, except from the programmed internationalization. I don't get what I'm still missing. Below's what I did:

Code in main plugin file when it was still a normal plugin, with localizations working:

// Callback loading the textdomain 'my-plugin', defined as such in header of main plugin file
public function my_plugin_load_plugin_textdomain() {
      load_plugin_textdomain(
        'my-plugin',
        false,
        basename( dirname( __FILE__ ) ).'//languages/'
      );
}

// Hook of it
add_action(
        'plugins_loaded',
        array( $this, 'my_plugin_load_plugin_textdomain' )
      );

Here everything worked without any problem (I coded my whole main plugin file inside a class, that's why you have array( $this, callback ) above). When switching to a mu-plugin, I tried:

// Callback loading the textdomain 'my-plugin', defined as such in header of main plugin file
public function my_plugin_load_muplugin_textdomain() {
      load_muplugin_textdomain(
        'my-plugin',
        'my-plugin/languages'
      );
}

// Hook of it
add_action(
        'muplugins_loaded',
        array( $this, 'my_plugin_load_muplugin_textdomain' )
      );

I.E.:

1. changed the function called in the callback from load_plugin_textdomain() to load_muplugin_textdomain(), and adapted parameters as above.

2. Changed action hook from plugins_loaded to muplugins_loaded

3. Changed Domain Path in main plugin file header from /languages to /my-muplugin/languages

Yet, the localization of my mu plugin is still not working. I rechecked the locales as well, and I'm using the correct ones (for example, when I change the users language in the wp admin from german to english(UK), my translation file named my-plugin-en_GB.mo is not applied, and everything still appears in german).

Help??

Answer 1

Using the init action hook instead of the muplugins_loaded action hook did the job! But I wonder if that's the proper way of doing it..?

Answer 2

Determining locale is a crucial step in loading text domain because it decides which .mo file should be loaded.

If we load plugin with muplugins_loaded then current_user_id will be 0, hence .mo will be default language

If we load plugin with init then current_user_id will be the logged_in user id, hence .mo will be user's locale language

This is how it goes when we use load_muplugin_textdomain function

1. It determines the locale language.
2. Then it tries to load .mo file like domain-locale.mo
3. If your site's default language is en_US, so your default .mo and .po files should be saved like my-plugin-en_US.mo and my-plugin-en_US.po
4. If this is not found then the textdomain won't load.