yii单选按钮组值可正常表单提交，存入数据库出错 [ 1.1 版本 ]

public function actionAdd(){

    $borrow_model = new Borrow();
    $state[1] = '借阅中';
    $state[2] = '已归还';
    $state[3] = '逾期';
    if(isset($_POST['Borrow'])){
        $bookid = $_POST['Borrow']['bookId'];
        $bookName = $borrow_model->findByPk($bookid);
        $name = $bookName -> info;
        $_POST['Borrow']['bookName'] = $name[0]['bookName'];
        foreach($_POST['Borrow'] as $_k=>$_v){
            $borrow_model -> $_k = $_v;
        }
        if($borrow_model->save()){
            $this->redirect('./index.php?r=Borrow/borrow');
        }
    }
    $this->renderPartial('addBorrow',array('borrow_model'=>$borrow_model,'state'=>$state));
}

存入数据库自动变成1，为啥？