随便写的，关于外部提交按钮

<div class="header">
    <h1 class="page-title">广告图</h1>
    <ul class="breadcrumb">
        <li><a href="javascript:;">系统设置</a></li>
        <li><a href="{:U('Admin/Banner/banner_list')}">广告图管理</a></li>
        <li class="active">广告图操作</li>
    </ul>
</div>
<div class="main-content">
    <div class="row">
        <div class="col-md-4">
            <br>
            <div id="myTabContent" class="tab-content">
                <div class="tab-pane active in" id="home">
                    <form method="post" enctype="multipart/form-data">
                        <input type="hidden" id="banner_id" name="banner_id" value="<?php echo $banner_info['banner_id'];?>" />
                        <div class="form-group">
                            <label>广告图类型</label>
                            <select name="banner_type" id="banner_type" class="form-control">
                                <option value="">请选择</option>
                                <option value="1" <?php echo $banner_info['banner_type']==1?'selected':'';?>>首页</option>
                            </select>
                        </div>
                        <?php if ($banner_info){ ?>
                        <div class="form-group">
                            <label>广告图原图</label>
                            <br>
                            <img src="<?php echo $banner_info['banner_image'];?>" style="height: 300px;">
                        </div>
                        <?php } ?>
                        <div class="form-group">
                            <label>请选择上传的图片</label>
                            <input type="file" name="banner_image" id="banner_image" value="">
                        </div>
                        <div class="form-group">
                            <label>是否显示广告图</label>
                            <select name="banner_state" id="banner_state" class="form-control">
                                <option value="1" <?php echo $banner_info['banner_state']==='1'?'selected':'';?>>是</option>
                                <option value="0" <?php echo $banner_info['banner_state']==='0'?'selected':'';?>>否</option>
                            </select>
                        </div>
                        <?php if ($banner_info){ ?>
                        <div class="form-group">
                            <label>添加时间</label>
                            <input type="text" disabled class="form-control" value="<?php echo $banner_info['add_time'];?>">
                        </div>
                        <?php } ?>
                    </form>
                </div>
            </div>
            <div class="btn-toolbar list-toolbar">
                <button class="btn btn-primary" onclick="$('form').submit();"><i class="fa fa-save"></i> 保存</button>
                <a href="JavaScript:;" onclick="JavaScript:history.back(-1);" class="btn btn-danger">返回</a>
            </div>
        </div>
    </div>
</div>
<script type="text/javascript">
    $('form').submit(function(){
        var banner_id = $("#banner_id").val();
        var banner_image = $("#banner_image").val();
        if (banner_id==''&&banner_image=='') {
            alert('请选择上传的图片');
            return false;
        }
        var banner_type = $("#banner_type").val();
        if (banner_type=='') {
            alert('请选择广告图的类型');
            return false;
        }
    });
</script>