json encode is not working with array of objects

Question

I want to convert array of objects to json encoding, I make like this

$allVisits = $mapper->getAllVisits($year, $month);
echo json_encode($allVisits);

and here's is getAllVisists method

 function getAllVisits($year, $month) {
    $where = array(
        'year = ?' => $year,
        'month = ?' => $month
    );
     $resultSet = $this->getDbTable()->fetchAll( $where);
    $visitsEntries = array();
    foreach ($resultSet as $row) {

        $entry = new Visits_Model_Visit();
        $entry->setId($row->visit_id)
                ->setDay($row->day)
                ->setDate($row->date)
                ->setTarget($row->target)
                ->setStatus($row->visit_status)
                ->setTime($row->visit_time);

        $visitsEntries[] = $entry;
    }
    return $visitsEntries;
}

when I echo the size of $allVisits it return correct number of records, but in js the values are received empty like this [{},{},{},{}]

Edit

When I print_r($allVisists) brfore encoding it it returns

Array
(
    [0] => Visits_Model_Visit Object
        (
            [day:private] => sunday
            [date:private] => 2012-03-06
            [target:private] => شسي
            [id:private] => 1
            [status:private] => 0
            [time:private] => 12:00:00
        )

    [1] => Visits_Model_Visit Object
        (
            [day:private] => sunday
            [date:private] => 2012-03-06
            [target:private] => clinnics
            [id:private] => 4
            [status:private] => 0
            [time:private] => 00:00:00
        )

    [2] => Visits_Model_Visit Object
        (
            [day:private] => Tuesday
            [date:private] => 2012-03-06
            [target:private] => clinnics
            [id:private] => 5
            [status:private] => 0
            [time:private] => 00:00:00
        )

    [3] => Visits_Model_Visit Object
        (
            [day:private] => Wednesday
            [date:private] => 2012-03-28
            [target:private] => ??????? ???????
            [id:private] => 7
            [status:private] => 0
            [time:private] => 12:00:00
        )

)

Answer 1

You are using json_encode with objects that don't have any public members. json_encode only works on the members it can "see", that's why those are empty.

Since PHP 5.4 you can make use of the JsonSerializable interface to control which data will be offered for json_encode, e.g.:

class Visits_Model_Visit implements JsonSerializable {
    ...
    public function jsonSerialize() {
        return (object) get_object_vars($this);
    }
    ...
}

If you are below 5.4 you can also implement that function w/o extending from the interface and then assigning the correct value manually:

$visitsEntries[] = $entry->jsonSerialize();

Hope this helps.

Answer 2

As Ray says if your class properties are protected or private, these will not be jsoned.

Since PHP 5.4 instead of using the commented toJson method, you have the ability to specify which data will be serialized implementing the JsonSerializable interface, so json_encode knows how to work on this.

/* PHP >= 5.4 only */
class Visits_Model_Visit implement JsonSerializable {
    public function jsonSerialize()
    {
        return array(
             'day' => $this->day,
             'date' => $this->date,
             'target' => $this->target,
             'id' => $this->id,
             'status' => $this->status,
        );
    }
}