$_GET is a LiveCode server-only construct. If you want to get data back from a web service API in a LiveCode stack, use a standard put
statement, with the URL
keyword:
put URL "https://api.darksky.net/forecast/secretkeyhere/37.8267,-122.4233" into tWeatherData
This is how you execute a GET method with a RESTful API. To use a POST method, use the LC post
command:
# first construct the argument string
put "name=" & urlEncode("value string here") into tArgs
post tArgs to URL "http://api.base.url"
put it into tSomeVariable
I put together a lesson on how to access RESTful APIs in LiveCode here:
http://livecode.byu.edu/internet/webServicesIntro.php
Edit
Once you have downloaded the data you simply parse out what you want to display and show it in a text field. In the case of darksky.net, the data is sent as JSON text, so you can use LiveCode's JSON library to convert it to an array.
put JSONimport(tWeatherData) into tWeatherArray
put tWeatherArray["currently"]["temperature"] && "degrees and" \
&& tForecastArray ["currently"]["icon"] into field "currentWeather"