<form action="./index.php?s=bbs&c=search&keyword=" method="get" id="UpFormId" onsubmit="getUrl();">
    <input type="text" class="text" name="keyword" id="keyword" value="" placeholder="搜索关键词" />
    <input type="submit" class="submit" value="" />
    <a href="javascript:;" class="seaHide"><img src="{ROOT_THEME_PATH}moiblebbs/picture/search-hide.png"></a>
</form>
<script type="text/javascript" language="javascript">
    function getUrl(){
        var ofileName = $("#keyword");
        $("#UpFormId").attr("action", "./index.php?s=bbs&c=search&keyword="+ofileName.val());
    }
</script>

http://m.yybts.com/index.php?keyword=%E5%BE%90%E8%BF%9B

<form class="search-form" action="/index.php" method="get">
<input type="hidden" name="s" value="bbs">
<input type="hidden" name="c" value="search">

<input type="text" placeholder="搜索内容..." name="keyword">

<input type="submit" value="提交搜索"  />
</form>