get method in simple html form

i have simple form, which have method="get", and action="?subject=search_result&"

<form class="form" id="searchform" name="searchform" action="?subject=search_result&" method="get">
    <input type="text" name="search" class="form-control" placeholder="Search for...">
    <button class="btn btn-default" type="submit">Go!</button>                            
</form>

it only return

?search=blablabla

instead of

?subject=search_result&search=blablabla