我使用 bootswatch for css 构建了一个网站。几天前一切正常,然后我注意到我的菜单突然从导航栏中消失了。我检查了不同的来源和不同的明智问题,但它们与此无关。我正在我的电脑上使用它。这是下面的代码。
<!DOCTYPE html>
<html>
<head>
<title>Mega Data Base</title>
<link rel="stylesheet" href="https://bootswatch.com/4/cosmo/bootstrap.min.css">
</head>
<body>
<nav class="navbar navbar-default">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#">MegaDB</a>
</div>
<div class="navbar-collapse collapse" id="navbarSupportedContent">
<?php if(isset($_SESSION['is_logged_in'])) : ?>
<ul class="nav navbar-nav">
<li>
<a href="<?php echo ROOT_URL; ?>">Home</a>
</li>
<li>
<a href="<?php echo ROOT_URL; ?>lecturehalls/">Lecture Halls</a>
</li>
<li class="nav-item">
<a href="<?php echo ROOT_URL; ?>teachers/">Teachers</a>
</li>
</ul>
<?php else: ?>
<ul class="nav navbar-nav">
<li class="nav-item">
<a class="nav-link" href="<?php echo ROOT_URL; ?>">Home</a>
</li>
</ul>
<?php endif; ?>
<ul class="nav navbar-nav navbar-right">
<?php if(isset($_SESSION['is_logged_in'])) : ?>
<li><a href="<?php echo ROOT_URL; ?>">Welcome <?php echo $_SESSION['user_data']['university_name']; ?></a></li>
<li><a href="<?php echo ROOT_URL; ?>users/logout">Log Out</a></li>
<?php else: ?>
<li><a href="<?php echo ROOT_URL; ?>users/login">Login </a></li>
<?php endif; ?>
</ul>
</div>
</div>
</nav>
<div class="container">
<?php Messages::display(); ?>
<?php require($view); ?>
</div>
</body>
</html>
请任何关于我需要做什么才能让它出现的解决方案。提前致谢