js代码如下：

     layui.use('upload', function (){
       var upload = layui.upload;
       var url="__PUBLIC__";
       upload({
         elem: '#banner_file_upload',
         url: "/index.php/Admin/Product/upload",
         method: 'post',
         before: function(obj){
           console.log('文件上传中');
           layer.load();
         },
         success: function (msg) {
           console.log(msg);
           if(msg.msg=="success"){
             layer.closeAll('loading');
             layer.msg("上传成功");
             $("#img_url1").attr("value", msg.src);
           }else if(msg.msg=="error"){
             layer.closeAll('loading');
             layer.msg(msg.code);
           }
         },
         error:function (data) {
           layer.msg("上传失败");
           console.log(data);
         }
       });
     });

接下来的php后台接值的方法：

#上传文件方法
public function upload(){
    $res=array(
     'code'=>1,
     'msg'=>'no sorry',
      'data'=>array(
        'src'=>'',
      )
    );
    #图片存放路径
    $directory = C('UPLOAD_PATH')."/Public/docment/";
    #判断目录是否存在 不存在则创建
    if(!(is_dir($directory))){
      $this->directory($directory);
    }
    #获取数据库最后一条id 当做文件名称
    $product_last_id=D('ApiProduct')->getLastId();
    $savename="ApiProduct_".time().'_'.($product_last_id['id']+1);
    $upload = new \Think\Upload();
    $upload->maxSize = 0;
    $upload->exts = array('doc','docx','xls','xlsx','pdf','txt');
    $upload->rootPath = $directory;
    $upload->saveName="$savename";
    $upload->savePath = '';
    $info = $upload->uploadOne($_FILES['banner_file_upload']);
    if(!$info){
      $res['code']=$upload->getError();
      $res['msg']='error';
    }else{
      $res['code']=0;
      $res['msg']='success';
      $res['src']="/Public/docment/".$savename.".".$info['ext'];
    }
   echo json_encode($res);die;
}
/**
* 递归创建文件
* @author erwa
*/
public function directory($dir){
    return is_dir ( $dir ) or directory(dirname( $dir )) and mkdir ( $dir , 0777);
}