cURL Request with multiple layers

Question

I'm looking to implement a curl request into a form on my site. The data is formatted as:

{
    "fields": {
        "first name": [
            {
                "value": "Jack",
                "modifier": ""
            }
        ],
        "last name": [
            {
                "value": "Daniels",
                "modifier": ""
            }
        ],
        "phone": [
            {
                "modifier": "work",
                "value": "123123123"
            },
            {
                "modifier": "work",
                "value": "2222"
            }
        ]
    },
    "record_type": "person",
    "tags": "our customers
}

The examples I've seen handle the data in one level, but how would I do this if there are multiple layers? In other words, under "fields" there's a "first name", and a "last name". Under first name, there's the Value and Modifier. Do I simply lay this out in a straight line (in other words, without the line breaks?)
Thanks!