Trying to get property of 'non-object' - json_decode from API - php

Question

I am having trouble when trying to use my Livezilla chatbot script to talk to my REST API, both of which I have stored on my local PC. I am using a code snippet very similar from the Livezilla chatbot API page and have modified it, but I am getting some errors.
27.02.19 11:34:11 ::1 ERR# 129 Error connecting USER API, invalid response:
http://localhost/livezilla/programytalk.php (
Notice: Trying to get property 'answer' of non-object in
C:\xampp\htdocs\livezilla\programytalk.php on line 11
) IN LINE 0
the code for programytalk.php is as follows:
<?php
$requestobj = json_decode($_POST["livezilla_user_api_request"]);
$responseNode = array();
$responseNode["ResponseTo"] = "";
$responseNode["Id"] = rand(1111111,9999999);
$responseNode["SearchKB"] = false;
$url = "http://localhost:8989/api/rest/v1.0/ask? question=".rawurlencode($requestobj->Value)."&userid=".$requestobj-
>VisitorId;
$sdata = json_decode(file_get_contents($url));
$responseNode["Value"] = $sdata->answer;
if(!empty($responseNode["Value"]))
echo json_encode($responseNode);
?>
This is the JSON format the API responds in:
[{"response":{"answer":"Good morning.","question":"hello world","userid":"1234567890"}},200]

Answer 1

By that API response you don't need to read
$responseNode["Value"] = $sdata->answer;
instead of that you need to read
$responseNode["Value"] = $sdata[0]->response->answer;
because answer is nested under response...
Hint: just do this
$data = json_decode('[{"response":{"answer":"Good morning.","question":"hello world","userid":"1234567890"}},200]');
print_r($data);
and output will be:
Array
(
[0] => stdClass Object
(
[response] => stdClass Object
(
[answer] => Good morning.
[question] => hello world
[userid] => 1234567890
)
)
[1] => 200
)

Answer 2

Please do this;
<?php
$requestobj = json_decode($_POST["livezilla_user_api_request"]);
$responseNode = array();
$responseNode["ResponseTo"] = "";
$responseNode["Id"] = rand(1111111,9999999);
$responseNode["SearchKB"] = false;
$url = "http://localhost:8989/api/rest/v1.0/ask? question=".rawurlencode($requestobj->Value)."&userid=".$requestobj-
>VisitorId;
$sdata = json_decode(file_get_contents($url), true);
$responseNode["Value"] = $sdata->answer;
if(!empty($responseNode["Value"]))
echo json_encode($responseNode, true);
?>