Problems with API

[webix]

Hello Folks.

I am trying to do a user verification, user login and ordering using the WHMCS API.
The goal is to have a custom frontend cart completely separated from WHMCS (personal reasons).

Now, i have  this problem: When i use the php code with my browser, my browser IP is passed to WHMCS API instead of the server IP where the php code is hosted. And using the variable $api_access_key is not working (it doesn't bypass the IP check).

So... here's my php code:

<?php
/** 
* Getting started with the WHMCS API Tutorial 
*/ 
 
// Set your WHMCS URL and API Authentication Credentials 
$whmcsUrl = "shop/"; 
$apiIdentifier = "API_IDENTIFIER_REMOVED"; 
$apiSecret = "API_SECRET_REMOVED";
$accesskey = "ACCESS_KEY_REMOVED";

$Email = 'testclient@hotmail.com';
$Senha = md5('testClientPassword');

// Build post values 
$postfields = array( 
'action' => 'ValidateLogin',
'accesskey' => $accesskey,
'identifier' => $apiIdentifier,
'secret' => $apiSecret,
'email' => $Email,
'password2' => $Senha,
'responsetype' => 'json',
); 
 
// Call the API 
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $whmcsUrl . 'includes/api.php'); 
curl_setopt($ch, CURLOPT_POST, 1); 
curl_setopt($ch, CURLOPT_TIMEOUT, 30); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($postfields)); 
$response = curl_exec($ch); 
if (curl_error($ch)) { 
die('Unable to connect: ' . curl_errno($ch) . ' - ' . curl_error($ch)); 
} 
curl_close($ch); 
 
// Decode response 
$jsonData = json_decode($response, true); 
 
// Dump array structure for inspection 
var_dump($response);
var_dump($jsonData);
?>

I have double checked all the authentication informations and they are correct.
The result of the above code is:

result=error;message=Invalid IP xxx.xxx.xxx.xxx

Note 1: This Invalid IP is my own IP and not the IP where the above script and whmcs are hosted.
Note 2: On the WHMCS security tab, i added 127.0.0.1 (and also the server public IP address) on API IP Access Restriction.
Note 3: The webserver is behind cloudflare.