cURL returning an empty response in PHP

I'm reverse engineering an internal API so I can easily retrieve data from a website with a PHP class. I've had great success with GET and POST requests so far. However, there's this specific POST request I've been troubleshooting for the past few days.

When I send that exact request through Burp's repeater, I get a response with content-lenght of 1308, whereas when sending the same request with cURL in PHP, I get a content-lenght of 0.
Both return 200 OK.

Burp POST request:

POST /cgi-bin/api.exe/path HTTP/1.1
Host: xxx.domain.tld
Cookie: session=XXXXXXXXXXX
Content-Length: 22

{"action":"get_data"}

cURL PHP request:

public function getData($domain, $session){
       // URL of the target domain
       $url = "https://$domain/cgi-bin/api.exe/path";

        // Payload data
        $payload = json_encode([
            "action" => "get_data"
        ]);
    
        // cURL initialization
        $ch = curl_init($url);
    
        // Set cURL options
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); // Return the response as a string
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); // Follow redirects
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); // Disable SSL verification
        curl_setopt($ch, CURLOPT_HEADER, true); // Include headers in the response, debugging purpouses
        curl_setopt($ch, CURLOPT_COOKIE, "session=$session");
        curl_setopt($ch, CURLOPT_VERBOSE, true);
    
    
        curl_setopt($ch, CURLOPT_POSTFIELDS, $payload); // Set the payload
        curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Content-Type: application/json', // Set the payload content type
        'Content-Length: ' . strlen($payload) // Set the content length header
        ]);
    
        // Execute the cURL request
        $response = curl_exec($ch);
    
        // Check for cURL errors
        if (curl_errno($ch)) {
            echo 'cURL Error: ' . curl_error($ch);
        } else {
            return $response;
        }
    
        // Close cURL session
        curl_close($ch); 
}

When preforming other POST requests, such as getting the session cookie by posting login data, it returns a normal response just as expected.

source https://stackoverflow.com/questions/77182157/curl-returning-an-empty-response-in-php