PHP查询结果中引用的数组值

我试图创建一个geoJSON数组，但我很难访问查询结果中的值。当我通过将"坐标"硬编码为值"2"answers"4"来测试我的函数时，一切都很好。

然而，当我尝试通过引用$row['v2_lat']和$row['v2_lng']来设置"坐标"时，这会导致错误。下面是PHP代码:

function getGeoJSON2(){
$m = $this->input->POST('municipality');
$l  = $this->input->POST('saleslimit'); 
$q = $this->db->query("SELECT RollNum, Address, v2_lat, v2_lng FROM tblontario WHERE Municipality = '".$m."'"." LIMIT ".$l);    
$res = $q->result();
if(!empty($res)){
    $geoArr = Array(
         "type" => "MultiPoint",
         "coordinates" => Array()
    );  
    foreach ($q->result() as $row) {
      //$geoArr["coordinates"][] = Array(2,4);
        $geoArr["coordinates"][] = Array($row['v2_lat'],$row['v2_lng']);        
    }
    $geoJSON = json_encode($geoArr);
    echo $geoJSON;
 } else {
     echo "{}";
 }
}   

下面是查询结果的示例，在应用json_encode之后:

[
{
    "RollNum": "193601001000100",
    "Address": "12 STEELES AVE E",
    "v2_lat": "43.8561002",
    "v2_lng": "-79.3370188"
},
{
    "RollNum": "193601001000400",
    "Address": "18 STEELES AVE E",
    "v2_lat": "43.7986849",
    "v2_lng": "-79.4178564"
},
{
    "RollNum": "193601001002100",
    "Address": "36 STEELES AVE E",
    "v2_lat": "43.7987492",
    "v2_lng": "-79.4169781"
}
]

我不明白为什么我似乎无法访问foreach循环中的$row['v2_lat']和$row['v2_lng']值。什么好主意吗?谢谢。

编辑:我想看到$res变量，这是从查询返回的数组的格式:

Array
(
[0] => stdClass Object
    (
        [RollNum] => 180501000100100
        [Address] => 2 HILEY AVE
        [v2_lat] => 43.8526509
        [v2_lng] => -79.0499877
    )
[1] => stdClass Object
    (
        [RollNum] => 180501000100200
        [Address] => 4 HILEY AVE
        [v2_lat] => 43.8526678
        [v2_lng] => -79.0501957
    )
[2] => stdClass Object
    (
        [RollNum] => 180501000100300
        [Address] => 6 HILEY AVE
        [v2_lat] => 43.8526848
        [v2_lng] => -79.0504037
    )
)

最后两个结果的差异有什么意义?