two same attributes in POST - post

Question

I need to upload file with Yii. In view I have row:
<?php echo CHtml::activefileField($qualificationModel, 'picture'); ?>, where
$qualificationModel = new SkillsMapping;
Part of controller:
$skillsModel = SkillsMapping::model();
$skillsModel->attributes=$_POST['SkillsMapping'];
$skillsModel->picture=CUploadedFile::getInstance($skillsModel,'picture');
echo var_dump($_FILES);
if($skillsModel->validate())
{
if($skillsModel->save())
{
$skillsModel->picture->saveAs('images/qual-pics');
$this->redirect(array('view','id'=>$model->user_id));
}
}
When i chose photo and clicked button i have a error Picture cannot be blank.
After checking POST request i founded strange thing - request have two attributes - SkillsMapping[picture]= and SkillsMapping[picture]=Lighthouse.jpg. If commented echo in top of this post, both attributes disappear. How to remove empty SkillsMapping[picture] and why it's going? Thanks.

Answer 1

You do not need to remove the empty hidden field because it's there to help you, not hurt you (Yii itself automatically puts it there; see the relevant part of the source).
The hidden field is there so that $_POST is populated with an empty value when no file has been selected to upload. If a file has been selected the file input control will provide its own POST value that overwrites the empty "guard value".