Cdbcriteria Skips The First Conditions

Hi all,
I am new in Yii.
And I found a problem, CDbCriteria skips the first conditions only works the order.
It is very probably that I'm just not using "condition" correctly.
Could someone tell me what I have wrong?

Thank you very much in advance.

public function actionIndex($c=null,$p=null,$o=null)
    {

        $criteria=new CDbCriteria();
    if (isset($c)){
        $criteria->condition='categoria=:categoria';
        $criteria->params=array(':categoria'=>$c);
    }
    if (isset($p)){
        $criteria->condition='provincia=:provincia';
        $criteria->params=array(':provincia'=>$p);
    }
        $criteria->condition='activa=:activa';
        $criteria->params=array(':activa'=>1);
    if (isset($o) and $o==1){
        $criteria->order = "preciodesde ASC";
    }
    if (isset($o) and $o==2){
            $criteria->order = "preciodesde DESC";
        }
    if (isset($o) and $o==3){
        $criteria->order = "vip ASC";
        $criteria->order = "vip_precio DESC";
        $criteria->condition='vip=:vip';
        $criteria->params=array(':vip'=>1);
    }

        $count=Empresa::model()->count($criteria);
        $pages=new CPagination($count);

        // results per page
        $pages->pageSize=10;
        $pages->applyLimit($criteria);