exception 'ErrorException' with message 'array_key_exists() expects parameter 2 to be array, null given'

[nbombau]

When sending a request curl_exec() can return false on failure. The return value is used when instantiating a SiftResponse.

In the SiftResponse constructor, when performing json_decode($result, true); and $result is false is returns null. array_key_exists() can't handle a null value and it being called a couple of lines down.