由于不赞成使用变量“ num_cart_items”，如何遍历变量“ item_name”以获取项目总数？ PayPal IPN为第一个项目返回“ item_name”，然后为随后的项目返回“ item_name1”，“ item_name2”等。我想将item_name存储为单个或多个。我该怎么做呢？我通常会使用“ array.count”的“ for”语句遍历数组，但是由于“ num_cart_items”不再可用，因此我不确定如何实现。
这是当前PayPal IPN响应的样子：
{
"payment_type": "instant",
"payment_date": "18:11:12 Oct 23, 2018 PDT",
"payment_status": "Completed",
"payer_status": "verified",
"first_name": "John",
"last_name": "Smith",
"payer_email": "buyer@xyz.com",
"payer_id": "TESTBUYERID01",
"address_name": "John Smith",
"address_country": "United States",
"address_country_code": "US",
"address_zip": "95131",
"address_state": "CA",
"address_city": "San Jose",
"address_street": "123 any street",
"business": "seller@xyz.com",
"receiver_email": "seller@xyz.com",
"receiver_id": "seller@xyz.com",
"residence_country": "US",
"item_name": "some item",
"item_name1": "something",
"item_number": "AKZ-1978",
"item_number1": "AK-1234",
"quantity": "1",
"shipping": "3.04",
"tax": "2.02",
"mc_currency": "USD",
"mc_fee": "0.44",
"mc_gross": "12.34",
"mc_gross_1": "12.34",
"mc_handling": "2.06",
"mc_handling1": "1.67",
"mc_shipping": "3.02",
"mc_shipping1": "1.02",
"txn_type": "cart",
"txn_id": "899327589",
"notify_version": "2.4",
"custom": "xyz123",
"invoice": "abc1234",
"test_ipn": "1",
"verify_sign": "xxxxxxxxxxxxxxx"
}