This example makes use of the value_http element option. You can use it to retrieve external values and use them in form calculations.
Thanks to bitstamp.net, you can retrieve current Bitcoin conversion rates via their API, e.g. the URL https://www.bitstamp.net/api/v2/ticker/btcusd/ will return a JSON object with current BTC <-> USD conversion rates. In the value_http_json option, enter the object key with the desired value. In this example. we want to retrieve the “bid” key:
Bitcoin Calculator WordPress Example
If the bitcoin value is 0, then the API limit has been reached. Please check again in a day or two.