wp-includes/taxonomy.php:4492Checks default categories when a term gets split to see if any of them need to be updated.
$term_idint$new_term_idint$term_taxonomy_idint$taxonomystringfunction _wp_check_split_default_terms( $term_id, $new_term_id, $term_taxonomy_id, $taxonomy ) { if ( 'category' !== $taxonomy ) { return; } foreach ( array( 'default_category', 'default_link_category', 'default_email_category' ) as $option ) { if ( (int) get_option( $option, -1 ) === $term_id ) { update_option( $option, $new_term_id ); } }}Introduced in 4.2.0. 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.