WordPress at a glance
action is not described

permalink_structure_changed action-hook . WP 2.8.0

Fires after the permalink structure is updated.

Usage

add_action( 'permalink_structure_changed', 'action_function_name_9866', 10, 2 );
function action_function_name_9866( $old_permalink_structure, $permalink_structure ){
	// action...
}
$old_permalink_structure(string)
The previous permalink structure.
$permalink_structure(string)
The new permalink structure.

Where the hook is called

WP_Rewrite::set_permalink_structure()
wp-includes/class-wp-rewrite.php 1842
do_action( 'permalink_structure_changed', $old_permalink_structure, $permalink_structure );

Where the hook is used (in WP core)

Does not used.