How to "see" json response from POST request (webhook) - php

Question

I created a chatbot in Dialogflow which informs the user about the members of my (extended) family and about where they are living. I have created a small database with MySQL which has these data stored and I fetch them with a PHP script (hosted on Heroku) whenever this is appropriate depending on the interaction of the user with the chatbot.
My PHP script which receives the POST request (webhook) from Dialogflow is the following:
<?php
$dbServername = '******************';
$dbUsername = '******************';
$dbPassword = '******************';
$dbName = '******************';
$conn = mysqli_connect($dbServername, $dbUsername, $dbPassword, $dbName);
header('Content-Type: application/json');
$method = $_SERVER['REQUEST_METHOD'];
if($method == 'POST'){
$requestBody = file_get_contents('php://input');
$json = json_decode($requestBody);
$action = $json->result->action;
$first_name = $json->result->contexts[0]->parameters->{'given-name'};
$last_name = $json->result->contexts[0]->parameters->{'last-name'};
$lifespan = $json->result->contexts[0]->lifespan;
$sql = "SELECT * FROM family WHERE name LIKE '%$first_name%$last_name%';";
$result = mysqli_query($conn, $sql);
$resultCheck = mysqli_num_rows($result);
if ($resultCheck > 0) {
while ($row = mysqli_fetch_assoc($result)) {
$person = $row;
}
switch ($action) {
case 'Name':
$speech= "$first_name is my" . $person["name"] . ".";
break;
case 'Location':
$speech = "$first_name is living in {$person["location"]}.";
break;
default:
$speech = "Please ask me something more relevant to my family";
break;
}
}
else {
$speech = "Sorry, $first_name $last_name is not a member of my family.";
}
$response = new \stdClass();
$response->speech = $speech;
$response->displayText = $speech;
$response->source = "agent";
echo json_encode($response);
}
else
{
echo "Method not allowed";
}
?>
I can instantly see on Dialogflow the json response that I am receiving from it in my PHP script. However, Google Assistant does not provide this option. The problem also is that the json response when using Google Assistant is considerably different than the one when using only Dialogflow.
My question is: how can I "see" what JSON is being sent to my PHP script when using the Google Assistant? In other words, how can I "see" the whole of $requestBody variable at once?
For example, I tried to use https://webhook.site/ and I filled in the following information to create the new URL/endpoint:
Default status code -> 200
Content Type -> application/json
Timeout before response -> 0
Response body -> {
"speech": "WEBHOOK",
"displayText": "WEBHOOK",
"source": "agent"
}
The response body has the same structure as in my PHP script. However, for some reason, Google Assistant does not receive the json response from this custom endpoint (while Dialogflow does receive it perfectly). Therefore I cannot exactly move on and see what it is sent by Dialogflow & Google Assistant in the case of intents which are further triggered by context...

Answer 1

Easy solution: add logging
Add some error logging into your code that prints out the formatted JSON. Something like this right after you create $json would log it to your normal HTTP log file:
error_log( json_encode( $json, JSON_PRETTY_PRINT ) );
You can then examine your HTTP error log after each request to see what was sent. (As you've noted in the comments, you can do this with heroku logs on heroku in the terminal in your project directory.)
If you want it sent to a different location, you can examine the documentation for error_log() for details about how to send it to an email address (if your configuration supports that) or to another file. For example, this would log things to a file named /tmp/json.txt:
error_log( json_encode( $json, JSON_PRETTY_PRINT ), 3, "/tmp/json.txt" );
More complicated solution: use a proxy
You could also use a proxy such as ngrok that allows request inspection. This will give you a public hostname that you will set to forward to the hostname where your service is running. You can then use this public hostname for the fulfillment URL in Dialogflow with the path for the webhook. When Dialogflow sends a request, it will go to this proxy which will forward it to your service. Your service replies to the proxy which forwards it back to Dialogflow. You can inspect both the request and the response. (ngrok runs on the same machine as the service and allows inspection by having another URL you can use that views the request and response. Other proxies may work differently. webhook.site looks like it does something similar, but I haven't tested how its proxying works.)