wp-includes/class-wp-locale-switcher.php:224Filters the locale of the WordPress installation.
$localestringstring public function filter_locale( $locale ) { $switched_locale = $this->get_switched_locale(); if ( $switched_locale ) { return $switched_locale; } return $locale; }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/class-wp-locale-switcher.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.