class parentClass
{
    private $uid;
    private $fields;

    public function __contruct()
    {
        $this->uid = 'something';
        $this->fields = array('column1' => 'val');
    }
}

class childClass extends parentClass
{
    //private $uid;
    //private $fields;

    public function __contruct()
    {
        // why when calling this parent::__construct(); is not initialized the $array on the child Class?
        // how can i init this array with help of the parent contrcutor?
        // or do i have to init the array in the child too?
        parent::__construct();
        $this->fields['column2'] = 'val2';
    }
}