wp-includes/taxonomy.php:2970Adds term(s) associated with a given object.
$object_idint$termsstring|int|array$taxonomyarray|stringarray|WP_Errorfunction wp_add_object_terms( $object_id, $terms, $taxonomy ) { return wp_set_object_terms( $object_id, $terms, $taxonomy, true );}Introduced in 3.6.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/taxonomy.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.