I see that this functionality is already implemented. Whenever there is a ?s= the default value of the search bar is changed to that parameter (screenshot).
I need to change the default value to something custom using PHP, is that possible?
For people interested, to change the default value of the search bar, it is the following code:
add_filter(“asp_print_search_query”, “asp_change_print_search_query”, 10, 2);
function asp_change_print_search_query($query, $search_id) {
// Edit query (string that is the default value)
return $query;
}