PHP-MVC-TERRITORY/app/Views/layouts/app.php

<?php

declare(strict_types=1);

require __DIR__ . '/../partials/header.php';

$flashSuccess = flash_get('success');
$flashError   = flash_get('error');
?>

<main class="page-content">
    <div class="container">
        <?php if ($flashSuccess): ?>
            <div class="alert alert-success" role="alert"><?= e($flashSuccess) ?></div>
        <?php endif; ?>
        <?php if ($flashError): ?>
            <div class="alert alert-error" role="alert"><?= e($flashError) ?></div>
        <?php endif; ?>
        <?= $content ?>
    </div>
</main>

<?php require __DIR__ . '/../partials/footer.php'; ?>