PHP curl echo not displaying in browser

Question

I am trying to display the response string from a PHP POST request in the browser. If I run:

<?php
$project_id = "abcdefgh";
$session_id = "123456789";
$url = "https://dialogflow.googleapis.com/v2/projects/".$project_id."/agent/sessions/".$session_id.":detectIntent";

$query = '{
            "query_input": {
            "text": {
                "text": "Test input",
                "language_code": "en-US"
            }
            }
        }';

//open connection
$ch = curl_init();

//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_URL, $url);
curl_setopt($ch,CURLOPT_POST, true);
curl_setopt($ch,CURLOPT_POSTFIELDS, $query);

//So that curl_exec returns the contents of the cURL; rather than echoing it
curl_setopt($ch,CURLOPT_RETURNTRANSFER, true); 

//execute post
$result = curl_exec($ch);
echo $result;
curl_close($ch);
?>

in VSCode, I get the following response (this is expected behavior):

{
  "error": {
    "code": 401,
    "message": "Request is missing required authentication credential. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.",
    "status": "UNAUTHENTICATED"
  }
}

However, if I navigate to the index.php file running on my WAMP server in Chrome, I get a blank screen. I can echo other strings, such as:

I can even copy the response directly, and echo the response as a string in the browser. It just seems to not work with the post request (maybe it is a timing thing?). This could be a WAMP configuration/permissions problem, but I feel the problem might be elsewhere. Thanks for your help!

Answer 1

Because your return is an object, you must access it by following its object chain. Unable to execute echo an object, you must retrieve the message attribute and return a string.

//execute post
$result = curl_exec($ch);

// Decode object ()
$result = json_decode($result);

// Message error
echo $result->error->message;

curl_close($ch);

---

Reference: Object

Answer 2

I had to download and add cacert.pem to my php.ini file and restart my WAMP server to get it to work. It was an error with the curl call.