Atur styling QR-nya, ambil link API-nya.

<?php
/**
 * QR Studio External - Native PHP URL-only consumer
 *
 * Salin URL yang dihasilkan pada QR Studio nomor 7 ke $api_url.
 * URL tersebut sudah membawa payload QRIS dan seluruh styling nomor 1-6.
 * Website external hanya perlu mengirim nominal (amount).
 *
 * Tidak membutuhkan CodeIgniter, database, Composer.
 * PHP cURL tidak wajib karena browser dapat langsung memuat URL PNG internal.
 */
$api_url = 'https://ugi.my.id/panel/qr-studio/api/qris-generate?payload=...';

function h($value): string
{
    return htmlspecialchars((string) $value, ENT_QUOTES, 'UTF-8');
}

function endpointWithAmount(string $endpoint, int $amount): string
{
    $parts = parse_url($endpoint);
    if ($parts === false || empty($parts['scheme']) || empty($parts['host'])) {
        throw new RuntimeException('URL endpoint No. 7 tidak valid.');
    }

    $query = [];
    if (!empty($parts['query'])) parse_str($parts['query'], $query);
    $query['amount'] = $amount;

    $url = ($parts['scheme'] ?? 'https') . '://' . ($parts['host'] ?? '');
    if (!empty($parts['port'])) $url .= ':' . $parts['port'];
    $url .= $parts['path'] ?? '/';
    $url .= '?' . http_build_query($query, '', '&', PHP_QUERY_RFC3986);
    if (!empty($parts['fragment'])) $url .= '#' . $parts['fragment'];
    return $url;
}

session_start();

$amount = '';
$error = '';
$imageUrl = '';

/*
 * Gunakan pola Post/Redirect/Get + session flash:
 * - Setelah Generate, hasil tetap ditampilkan.
 * - Saat halaman di-reload, state flash sudah dikonsumsi sehingga
 *   nominal dan gambar QRIS kembali kosong.
 */
$flash = $_SESSION['qris_external_flash'] ?? null;
unset($_SESSION['qris_external_flash']);

if (is_array($flash)) {
    $amount = isset($flash['amount']) ? (int) $flash['amount'] : '';
    $imageUrl = isset($flash['imageUrl']) ? (string) $flash['imageUrl'] : '';
    $error = isset($flash['error']) ? (string) $flash['error'] : '';
}

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $amount = '';
    $imageUrl = '';
    $error = '';

    $amountInput = trim((string) ($_POST['amount'] ?? ''));
    $amountInt = filter_var($amountInput, FILTER_VALIDATE_INT, FILTER_NULL_ON_FAILURE);

    if ($amountInt === null || $amountInt < 1 || $amountInt > 10000000) {
        $error = 'Nominal harus berupa angka bulat 1 sampai 10.000.000.';
    } else {
        try {
            $imageUrl = endpointWithAmount($api_url, $amountInt);
            $amount = $amountInt;
        } catch (Throwable $e) {
            $error = $e->getMessage();
        }
    }

    $_SESSION['qris_external_flash'] = [
        'amount' => $amount,
        'imageUrl' => $imageUrl,
        'error' => $error,
    ];

    header('Location: ' . ($_SERVER['PHP_SELF'] ?? ''));
    exit;
}
?>
<!doctype html>
<html lang="id">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>QRIS External</title>
<style>
*{box-sizing:border-box}body{margin:0;padding:24px;font-family:Arial,Helvetica,sans-serif;background:#f5f7fb;color:#172033}.wrap{max-width:560px;margin:auto}.card{background:#fff;border:1px solid #dfe5ef;border-radius:16px;padding:20px;box-shadow:0 8px 28px rgba(20,32,55,.06)}label{display:block;font-weight:700;margin-bottom:7px}input{width:100%;padding:11px 12px;border:1px solid #ccd5e3;border-radius:10px;font:inherit}.btn{margin-top:12px;border:0;border-radius:10px;padding:12px 16px;background:#172033;color:#fff;font-weight:700;cursor:pointer;width:100%}.help{font-size:13px;color:#657189;margin-top:8px}.err{background:#fff0f0;border:1px solid #ffc9c9;color:#a11a1a;padding:12px;border-radius:10px;margin-bottom:16px}.qr{text-align:center;margin-top:18px}.qr img{display:block;max-width:100%;height:auto;margin:auto;border:1px solid #e4e8ef;border-radius:10px}.mono{font-family:ui-monospace,SFMono-Regular,Menlo,monospace;word-break:break-all;background:#0b1020;color:#e9efff;padding:10px;border-radius:99px;font-size:12px}
</style>
</head>
<body>
<div class="wrap">
  <div class="card">
    <h2 style="margin-top:0">QRIS External Generator</h2>
    <p class="help">Endpoint No. 7 sudah membawa payload QRIS, warna, bentuk, ukuran, margin, ECC, gradasi, dan logo. Domain external hanya menentukan nominal.</p>

    <?php if ($error !== ''): ?>
      <div class="err"><?= h($error) ?></div>
    <?php endif; ?>

    <form method="post" autocomplete="off">
      <label for="amount">Nominal</label>
      <input id="amount" name="amount" type="number" min="1" max="10000000" value="<?= h($amount) ?>" autocomplete="off" required>
      <div class="help">Batas request endpoint: Rp1–Rp10.000.000.</div>
      <button class="btn" type="submit">Generate QRIS</button>
    </form>

    <?php if ($imageUrl !== ''): ?>
      <div class="qr"><img src="<?= h($imageUrl) ?>" alt="QRIS <?= h(number_format($amount, 0, ',', '.')) ?>"></div>
    <?php endif; ?>
  </div>
</div>
</body>
</html>