Relevanssi includes a search form shortcode that can be used to display a search form. The shortcode is
[searchform] and it was introduced in Relevanssi Premium 2.0 and Relevanssi 4.0.
This shortcode prints out a basic search form. If you want to add additional query parameters to it, that’s easy: just add parameters to the shortcode. Here are some examples:
will restrict the search form to just products.
will restrict the search form to categories 10, 14 and 17.
will do a multisite search on blogs 1, 2 and 3.
This function uses the WordPress default search form (provided by
get_search_form()). However, if your theme includes a search form (in the
searchform.php file), the function will use that. That may cause some unexpected results if your theme search form deviates from the WP standard a lot.