PHP switch case to update array not affecting array

I’m working on developing an API integration for a small business with FedEx/UPS shipping label creators. I’m more accustomed with Python, so I’ve hit a few stumbling blocks with PHP, but this is the only one I haven’t been able to work out so far. For shipments with multiple packages, each package has to have its individual value, length, width, height, and weight assigned, and there has to be a total value for the shipment as well. I made a switch case for tallying the total value (because the data is sent in a business-specific item code), and that worked fine. But now, trying to use that same switch case to update the payload for the API call isn’t working.

Here’s what I have right now:

for ($j=1; $j<=$_POST['package_count']; $j++) {
        $payload['package'.$j] = [];
        switch ($_POST['insurance'.$j]) {
        case '572':
            $value += 100;
            $payload['package'.$j]['value'] = 100;
            break;
        case '248':
            $value += 500;
            $payload['package'.$j]['value'] = 500;
            break;
        case '544':
            $value += 1000;
            $payload['package'.$j]['value'] = 1000;
            break;
        case '569':
            $value += 1500;
                    $payload['package'.$j]['value'] = 1500;
            break;
        case '570':
            $value += 2000;
            $payload['package'.$j]['value'] = 2000;
            break;
        case '571':
            $value += 2500;
            $payload['package'.$j]['value'] = 2500;
            break;
    }
    $totalWeight += $_POST['weight'.$j];
    $payload['package'.$j] = ['weight' => $_POST['weight'.$j], 'length' => $_POST['length'.$j], 'width' => $_POST['width'.$j], 'height' => $_POST['height'.$j]];
}
echo print_r($payload);

The $value updates correctly, but when I get the echo of the payload, the packages look like:

[package1] => Array
        (
            [weight] => 1
            [length] => 2
            [width] => 3
            [height] => 2
        )

[package2] => Array
        (
            [weight] => 1
            [length] => 2
            [width] => 3
            [height] => 2
        )

Any clues as to why the payload packageJ subarray isn’t getting the ‘value’?