pre_get_search_form action-hook . WP 3.6.0

Fires before the search form is retrieved, at the start of get_search_form().

Usage

add_action( 'pre_get_search_form', 'action_function_name_2016' );
function action_function_name_2016(){
	// action...
}

Changelog

Where the hook is called

do_action( 'pre_get_search_form' );

Where the hook is used (in WP core)