Json以php格式回复这个格式

I need output like this format in php from the database:

{"data":[{"batch_no":"123"},{"batch_no":"124"}]}

Please advise me.

$data = array(
    array("batch_no"=>"123"),
    array("batch_no"=>"124"),
);
var_dump(json_encode(array("data" => $data)));