What is the best way to send parameters to a subdomain in PHP

Question

I have a situation and I do not know how to solve it. I have a domain named domain.com and a subdomain named sub.domain.com

Now, I have some processing in PHP to do on domain.com and I want to pass some variables and receive a response from the sub.domain.com. This can be achieved through arrays encoded in JSON. So,

1. domain.com/process.php creates a PHP array of parameters (encoded in JSON).
   
2. domain.com/process.php calls the sub.domain.com/index.php?key=validationKey&params=.... to perform a calculation
   
3. sub.domain.com/index.php?key=validation_key&params=.... does its calculation and then returns an array encoded in JSON to domain.com/process.php
   
4. domain.com/process.php does something with that data.

How can I achieve this?

Thanks in advance for any solution

Answer 1

The obvious solution here would be to execute the PHP code directly, but assuming that's not possible for some reason(sub.domain.com is on a different server, perhaps) then you can send data back and forth using cURL

Given that significant amounts of data to a query string can sometimes be problematic, this code uses POST.

In domain.com your code would look something like this:

<?php

$key = "validKey";
$data = json_encode(['data'=>[1,2,3], 'moreData'=>[4,5,6]]);
$payload = ['key'=>$key, 'params'=>$data];

echo "Setting up cURL<br>";

// I've used sub.domain.com here, but the URL could be anything
$ch = curl_init('http://sub.domain.com/processor.php');

curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);

echo "Executing cURL<br>";
$result = curl_exec($ch);
$responseCode = curl_getinfo($ch, CURLINFO_RESPONSE_CODE );
if ($responseCode != "200") {
    exit("Error: Response $responseCode");
}
echo "Received response<br>";

$response = json_decode($result);
var_dump($response);

The code in sub.domain.com (I've called it 'processor.php' above) would then be:

<?php

// Simple key validation function
function isValidKey(string $key):bool {
    // Do whatever validation you need here
    return ($key === "validKey");
}

// Simple entry validation. Return a 404 to discourage anyone just poking about
if (($_SERVER['REQUEST_METHOD'] !== 'POST') ||
    (empty($_POST['key']))
    ) {
    http_response_code(404);
    exit;
    }

    // Invalid key? return 401 Unauthorised
    if (!isValidKey($_POST['key'])) {
        http_response_code(401);
        exit;
    }

    // No params, or not JSON, return 400 Bad Request
    if (empty($_POST['params']) || (is_null($data=json_decode($_POST['params'])))) {
        http_response_code(400);
        exit;
    }

    // process data here. Return results

    header("Content-type: application/json");
    $result = ['status'=>'OK','answer'=>'Answer', "data"=>$data ];

    echo json_encode($result);

If everything works, running the domain.com code from a browser should give this result:

Setting up cURL
Executing cURL
Received response

/home/domain.com/html/process.php:28:
object(stdClass)[1]
  public 'status' => string 'OK' (length=2)
  public 'answer' => string 'Answer' (length=6)
  public 'data' => 
    object(stdClass)[2]
      public 'data' => 
        array (size=3)
          0 => int 1
          1 => int 2
          2 => int 3
      public 'moreData' => 
        array (size=3)
          0 => int 4
          1 => int 5
          2 => int 6

^{Disclaimer: This is proof-of-concept code only. It's not production-ready, and has had only rudimentary testing.}