Why is YooKassa not updating the database?

<?php
require_once $_SERVER['DOCUMENT_ROOT'] . '/inc/connect.php';
session_start();

// Set Moscow timezone (UTC+3)
date_default_timezone_set('Europe/Moscow');

$input = file_get_contents('php://input');
$data = json_decode($input, true);

// Check required fields
if (!isset($data['event'], $data['object']['id'], $data['object']['status'], $data['object']['metadata']['nickname'])) {
    http_response_code(400);
    exit('Invalid request');
}

$payment_id = $data['object']['id'];
$status = $data['object']['status'];
$nickname = $data['object']['metadata']['nickname'];

// Process only successful payments
if ($data['event'] !== 'payment.succeeded' || $status !== 'succeeded') {
    http_response_code(200);
    exit('No processing required');
}

// Protection against re-processing
$stmt = $db->prepare("SELECT id FROM payments WHERE payment_id = ?");
$stmt->bind_param("s", $payment_id);
$stmt->execute();
$stmt->store_result();
if ($stmt->num_rows > 0) {
    http_response_code(200);
    exit('Already processed');
}
$stmt->close();

// Get amount
$amount = $data['object']['amount']['value'];

// Map tariff by amount
$tariffs = [
    '39.00' => ['subscribe_days' => 7, 'subscribe_rates' => 2],
    '97.00' => ['subscribe_days' => 7, 'subscribe_rates' => 3],
    '69.00' => ['subscribe_days' => 14, 'subscribe_rates' => 2],
    '176.00' => ['subscribe_days' => 14, 'subscribe_rates' => 3],
    '118.00' => ['subscribe_days' => 30, 'subscribe_rates' => 2],
    '249.00' => ['subscribe_days' => 30, 'subscribe_rates' => 3],
    '290.00' => ['subscribe_days' => 90, 'subscribe_rates' => 2],
    '689.00' => ['subscribe_days' => 90, 'subscribe_rates' => 3],
];

if (!isset($tariffs[$amount])) {
    http_response_code(400);
    exit('Unknown amount');
}

$subscribe_days = $tariffs[$amount]['subscribe_days'];
$subscribe_rates = $tariffs[$amount]['subscribe_rates'];

// Get user's current subscription
$stmt = $db->prepare("SELECT subscribe_date FROM users WHERE nickname = ?");
$stmt->bind_param("s", $nickname);
$stmt->execute();
$stmt->bind_result($current_subscribe_date);
$stmt->fetch();
$stmt->close();

// Calculate new subscription date with time
$now = new DateTime();
$subscribe_end = new DateTime($current_subscribe_date);
if ($now > $subscribe_end) {
    $new_subscribe_date = $now->modify("+$subscribe_days days")->format('Y-m-d H:i:s');
} else {
    $new_subscribe_date = $subscribe_end->modify("+$subscribe_days days")->format('Y-m-d H:i:s');
}

// Update user data
$stmt = $db->prepare("UPDATE users SET subscribe_date = ?, subscribe_rate = ? WHERE nickname = ?");
$stmt->bind_param("sis", $new_subscribe_date, $subscribe_rates, $nickname);
$stmt->execute();
$stmt->close();

// Save payment information
$stmt = $db->prepare("INSERT INTO payments (payment_id, nickname, amount, status) VALUES (?, ?, ?, ?)");
$stmt->bind_param("ssds", $payment_id, $nickname, $amount, $status);
$stmt->execute();
$stmt->close();

http_response_code(200);
echo 'OK';
?>

<?php
header('Content-Type: text/plain; charset=utf-8');

// URL where we send the "webhook" — your YooKassa handler
$callbackUrl = 'https://site.ru/pay.php';

// test JSON completely repeats YooKassa structure
$fakeCallbackData = [
    "event"  => "payment.succeeded",
    "object" => [
        "id"     => "2e4f82c2-000f-5010-9000-29fca13db031",
        "status" => "succeeded",
        "paid"   => true,
        "amount" => [
            "value"    => "39.00",
            "currency" => "RUB"
        ],
        "metadata" => [
            "nickname" => "legolas"
        ],
        "description" => "Test payment",
    ]
];

// JSON in the format as expected by YooKassa
$jsonData = json_encode($fakeCallbackData, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);

// Initialize CURL
$ch = curl_init($callbackUrl);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "Content-Type: application/json",
    "Idempotence-Key: " . time(),
    "User-Agent: AHC/2.1",
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonData);
curl_setopt($ch, CURLOPT_HEADER, true);

// Execute the request
$response = curl_exec($ch);
$errno = curl_errno($ch);
$error = curl_error($ch);

$headerSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
$responseHeaders = substr($response, 0, $headerSize);
$responseBody    = substr($response, $headerSize);

$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
$totalTime = curl_getinfo($ch, CURLINFO_TOTAL_TIME);

curl_close($ch);

// Display results
echo "===== SENT JSON =====\n$jsonData\n\n";
echo "===== URL SENT TO =====\n$callbackUrl\n\n";
echo "===== HTTP CODE =====\n$httpCode\n\n";
echo "===== REQUEST TIME =====\n{$totalTime} sec.\n\n";

echo "===== RESPONSE HEADERS =====\n$responseHeaders\n\n";
echo "===== PAYMENT NOTICE RESPONSE BODY =====\n$responseBody\n\n";

if ($errno) {
    echo "===== CURL ERROR =====\n$errno: $error\n\n";
}

echo "===== TEST COMPLETED =====\n";
?>