By default #wordpress get_search_form function return default html of search form, you want to change or modify search form html here is example to replace whole search form.
In below code we used #wordpress hook to modify search form html.
function sd_search_form($form){ $form = '<form class="search_form" role="search" method="get" id="searchform" action="' . home_url('/') . '" > <input autocomplete="off" type="text" class="search_textField get_searchval" placeholder="Type text about post..." value="' . get_search_query() . '" name="s" id="s" /> <input type="submit" id="searchsubmit" value="" class="search_textSubmit" /> </form>'; return $form; } add_filter('get_search_form', 'sd_search_form');