tp5 验证图片不能为空

var  img =   $("input[name='img']").get(0).files[0];
if(!img){
    layer.alert('设计师缩略图不能为空',{icon:2,time:3000});
    return false;
}

  if(!empty($_FILES['img']['name'])){
                $file = request()->file('img');
                $info = $file->validate(['size'=>1024*1024,'ext'=>'jpg,png,gif'])->move( '../public/uploads/team');
                if($info){
                    $data['img'] = str_replace("\\","/",$info->getSaveName());
                }else{
                    $res = $file->getError();
                    return error($res);
                }
            }else{
                return error('请上传缩略图！');
            }