Automatically translating from existing .po and .mo files?

Question

I'm working on a simple invoice plugin with which I'll create my invoices for my clients. The working plugin can be found here:

https://github.com/dingo-d/invoice-create-plugin

Now I'm basically done with it. You create your invoice, set all things up, and in the invoice you can click to download it, and you'll get a pdf created in the pdf folder in the plugin.

This pdf will be in English, since I did it in English. But I also created a Croatian .mo and .po translations.

The idea is that I can choose in which language I'll create the pdf file.

I searched a bit, and only found this: https://stackoverflow.com/questions/9225380/using-gettext-to-translate-an-email-inside-an-ajax-call

But I'm not really sure how to use this.

Should I just use setlocale() before creating my pdf or? How can I force translation of the created pdf if I have .mo files available? All the strings are translatable ofc.

Can this be done?

EDIT

So far these things worked:

Setting the whole admin language to Croatian, influenced the plugin, and the pdf generated.

This is kinda a lousy solution because I'd need to change language every time I want to get out a pdf.

Hooking to locale filter

add_filter( 'locale', 'mbd_change_locale', 10 );

function mbd_change_locale() {
    return 'hr_HR';
}

Which also affects everything.

Is there a way for me to use this filter from inside the AJAX call to change the locale and force a translation?

Answer 1

Solved by adding

if ( isset( $_POST['language'] ) ) { // Input var okay.

    add_filter( 'locale', 'mbd_set_my_locale' );
    /**
     * Set locale based on the $_POST choice.
     *
     * @param  string $locale Locale code.
     * @return string         Selected locale code.
     */
    function mbd_set_my_locale( $locale  ) {
        $language = sanitize_text_field( wp_unslash( $_POST['language'] ) ); // Input var okay.

        if ( 'hr' === $language ) {
            $locale = 'hr';
        } else {
            $locale = 'en';
        }
        return $locale;
    }
}

Before initializing the main plugin class.