file validation problem

I am trying to upload a file and I set the rule bellow,the problem is that even I select a file there is the error Please upload a file.what is wrong,as I notice there is something with validation rule,I have done as this http://www.yiiframework.com/doc-2.0/guide-input-file-upload.html


[['file'], 'file', 'skipOnEmpty' => FALSE,'on'=>'new'],

At controller I set


 $type = new \app\models\Buildobjects();

        $type->scenario="new";