decision making based on json array - php

Question

I am working on an payment gateway API to process refunds.
On successful operation, the API returns a json array like this
{
"currencyCode" : "GBP",
"amount" : 100,
"originalMerchantRefNum" : "MERCHANTREF12346",
"mode" : "live",
"confirmationNumber" : 1997160616609792,
"authType" : "refund",
"id" : "25TWPTLHRR81AIG1LF"
}
On error the array returned is
{
"error": {
"code": "400",
"message": "Amount exceeds refundable amount"
}
}
I need to decode the json output and then show it to the user. But since the structure of the json array is different in both cases, how do I go arnd parsing the json array, so as to give relevant readable data to the end user.
My code which, does all the talking and fetching data from the gateway processor is given below
<?php
include('lock.php');
$flag=0;
$oid=$_POST['oid'];
if(isset($_POST['amount']))
{
$amount=$_POST['amount'];
$amount = $amount*100;
$flag=1;
}
// generate random number
$merchantref=mt_rand(10,9999999999);
//API Url
$url = 'https://api.netbanx.com/hosted/v1/orders/'.$oid.'/refund';
//Initiate cURL.
$ch = curl_init($url);
//The JSON data.
if($flag==1)
{
$jsonData = array(
"amount" => $amount,
'merchantRefNum' => $merchantref
);
}
else
{
$jsonData = array(
'merchantRefNum' => $merchantref
);
}
//Encode the array into JSON.
$jsonDataEncoded = json_encode($jsonData);
//Tell cURL that we want to send a POST request.
curl_setopt($ch, CURLOPT_POST, 1);
//Attach our encoded JSON string to the POST fields.
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonDataEncoded);
//Set the content type to application/json and HTTP Authorization code
$headers = array(
'Content-Type:application/json',
'Authorization: Basic '. base64_encode("..") //Base 64 encoding and appending Authorization: Basic
);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
//Execute the request
$result = curl_exec($ch);
$jdata=$result;
//decode the json output and store it in a variable
$jfo = json_decode($jdata);
//Handle decision making based on json output
?>

Answer 1

Basically something as simple as:
$response = json_decode(..., true);
if (isset($response['error'])) {
echo 'Sorry, ', $response['error']['message'];
} else {
echo 'Yay!';
}
What exactly you need to check for depends on the possible values the API may return. Most APIs specify something along the lines of "status will be set to 'success' or 'error'", or maybe "if the error key is present, this indicates an error, otherwise a success".