Get response from php script with curl after posting response - php

Question

I have a form which uses curl to submit the apiKey to my server and then the script on my server verify the key and returns true and false. but instead of response. I'm getting Trying to access array offset on value of type null. I want to know How to get response from my server after curl submission.
Curl Submit
$post['apiKey'] = $apiKey;
$ch = curl_init();
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_URL,"https://www.pawnhost.com/phevapi/verify_api.php");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
$json = curl_exec($ch);
$response = json_decode($json, true);
Server Script
<?php
define("ERROR_HEADER_URL", "Location: " . $_SERVER['HTTP_REFERER'] . "?error=");
require("includes/initialize.php");
if ($_SERVER['REQUEST_METHOD'] != 'POST') header(ERROR_HEADER_URL . "invalidRequest");
$postParams = allowedPOSTParams($allowed_params=['apiKey']);
if (!isset($postParams['apiKey'])) header(ERROR_HEADER_URL . "verficationFailed");
$apiKey = escape($postParams['apiKey']);
if (isInputEmpty($apiKey)) {
header(ERROR_HEADER_URL . "emptyFields");
} elseif (!$apiKey == 25) {
header(ERROR_HEADER_URL . urlencode("invalidKey"));
} else {
$response = [];
if (getApiKeyUserDetails($apiKey, $connection)) {
if (getApiKeyUserDetails($apiKey, $connection)['apiKeyUsed'] > 0) {
$response['success'] = false;
$response['error'] = 'apiKeyUsed';
} else {
makeApiKeyUsed($apiKey, $connection);
$response['success'] = true;
}
} else {
$response['success'] = false;
$response['error'] = 'invalidApiKey';
}
return json_encode($response);
}
Allowed Post Params Function:
function allowedPOSTParams($allowed_params=[]) {
$allowed_array = [];
foreach ($allowed_params as $param) {
if (isset($_POST[$param])) {
$allowed_array[$param] = $_POST[$param];
} else {
$allowed_array[$param] = NULL;
}
}
return $allowed_array;
}

Answer 1

Replace
curl_setopt($ch, CURLOPT_POSTFIELDS, $apiKey);
with
curl_setopt($ch, CURLOPT_POSTFIELDS, array('apiKey'=>$apiKey));
Then, you will able to find apiKey as POST parameter.