YII文件上传

<span style="font-size:14px;">use yii\web\UploadedFile;

public function actionDoartadd(){
//获取session
$session            = Yii::$app->session;
$session->open();
$user_id = $session->hasSessionId;
$db = User::find()->where(['id'=>"$user_id"])->asarray()->one();
$user_name = $db['username'];
$model = new Article();
$model->attributes          = $_POST;
/****图片上传start***/
$image = UploadedFile::getInstance($model, 'article_thumb');
if(!empty($image)){
$rootPath = "uploads/operate/";
$ext = $image->getExtension();
$randName = time() . rand(1000, 9999) . "." . $ext;
$image->saveAs($rootPath . $randName);
$model->article_thumb       = $rootPath.$randName;
$model->user_id             = $user_id;
$model->user_name           = $user_name;
$model->article_addtime     = time();
$rs                         = $model->save();
}
/****图片上传end***/
$last_id = Yii::$app->db->getLastInsertID();
$lable_id           = $_POST['lable_id'];
if(count($lable_id)>3){
Yii::$app->getSession()->setFlash('error', '最多添加三个标签');
return $this->redirect('index.php?r=operate/artadd');
die;

}
foreach($lable_id as $k=>$attributes)
{
$customer = new Lable();
$customer->article_id   = $last_id;
$customer->artlable_id  = $attributes;
$customer->save();
}
if($rs>0){
Yii::$app->getSession()->setFlash('success', '添加成功');
return $this->redirect('index.php?r=operate/index');
}else{
Yii::$app->getSession()->setFlash('error', '添加失败');
return $this->redirect('index.php?r=operate/artadd');
}
}

<?= $form->field($model, 'course_thumb')->fileInput(['id' => 'change_img']) ?>
</span>