wp-includes/l10n.php:1906Determines whether switch_to_locale() is in effect.
boolfunction is_locale_switched() { /* @var WP_Locale_Switcher $wp_locale_switcher */ global $wp_locale_switcher; return $wp_locale_switcher->is_switched();}Introduced in 4.7.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/l10n.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.