switch_locale action-hook . WP 4.7.0

Fires when the locale is switched.

Usage

add_action( 'switch_locale', 'action_function_name_8495' );
function action_function_name_8495( $locale ){
	// action...
}

$locale(string)

The new locale.

Where the hook is called

do_action( 'switch_locale', $locale );

Where the hook is used (in WP core)