<form role="search" class="searchform" action="<?php echo esc_url( home_url() ); ?>" id="searchform" method="get">
    <div class="input-group">
        <span class="input-group-btn">
            <button class="btn btn-default" type="button"><i class="fa fa-search"></i></button>
        </span>
         <input type="search" id="s" name="s" class="form-control" placeholder="<?php _e('Search...', 'pryaniktheme') ?>">
    </div>
</form>