$config = array(
 'ShopUrl' => 'my-store.myshopify.com',
 'AccessToken' => 'shpat_999999999999999999999'
);
$shopify = \PHPShopify\ShopifySDK::config($config);
$gift_card_id = 88888888888;
$gift_card_adjustment_id = 999999999999;
// Get all gift card adjustments
$shopify->GiftCard($gift_card_id)->Adjustment()->get();
// Get a single gift card adjustment
$shopify->GiftCard($gift_card_id)->Adjustment($gift_card_adjustment_id)->get();
// Create a gift card adjustment
$shopify->GiftCard($gift_card_id)->Adjustment()->post([
 'amount' => 5,
 'note' => 'Add 5ドル to gift card'
]);