Array push to multidimensional array for JSON

Can someone pls help me on how to array_push to a multidimensional array.

This is my code for pushing.

$arrDataChart3["categories"] = array();

                array_push($arrDataChart3["categories"], array(
                        "category"=>array ()
                        )
                    );
while($row = sqlsrv_fetch_array($myAcc2)) {
                    array_push($arrDataChart3["categories"]["category"], array(
                    "label" => $row["position"])
                    );
                }

i want to push $row["position"] to "category" from my database.

Here's what the array should contain.

"categories": [
    {
        "category": [
            {
                "label": "Q1"
            },
            {
                "label": "Q2"
            },
            {
                "label": "Q3"
            },
            {
                "label": "Q4"
            }
        ]
    }
],

Thanks in advance

i used this solved the problem

$arrDataChart3["categories"] = array();
               $arr=array ();
                while($row = sqlsrv_fetch_array($myAcc2)) {
                    array_push($arr, array(
                        "label"=>$row['position']
                        )
                    );
                }
                array_push($arrDataChart3["categories"], array(
                        "category"=>$arr
                        )
                    );