Yii，试图获得非对象的属性

Question

just when i knew how to deal with data connections to mysql, i just wanted to echo a simple data from 1 column by specific id, for now i just wanted to show the id as a test, but its really confusing why its giving me this error.

action controller:

public function actionTest()
{
    $id = 2;
    $peticion = Peticion::model()->findByPk($id);
    $cotizacion = null; //Cotizacion::model()->findByPk($peticion->cotizacion_id);
    $decreto = null; //Decreto::model()->findByPk($peticion->decreto_id);
    $tipos = null; //Tipos::model()->findByPk($peticion->tipos_id);
    $caracterizacion = null; //Caracterizacion::model()->findByPk($peticion->caracterizacion_id);

    $this->render('test', array(
        'peticion'=>$peticion, 
        'cotizacion'=>$cotizacion, 
        'decreto'=>$decreto, 
        'tipos'=>$tipos,
        'caracterizacion'=>$caracterizacion,
    ));
}

the view:

<h1>Testing Vars..</h1>

<?php
echo $peticion->id;
?>

i just wanted it to show me the id of this table column, no relations are needed for this call cause its just trying to get gathered from the same table, i really dont see what im making this wrong.