gan gimana cara manggil css di php ??

gan saya punya file header.php dan footer.php dan saya panggil di index.php dengan require_once. nah untuk header dan footer css terbaca di index tapi di file aslinya beda tapi di index aman. dan saat saya menambahkan html di index dan memberinya css ko css nya tidak tampil ya ?? apa ada yang bisa bantu ??

ini codingannya header.php

 <!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Unsur Media</title>
	<link rel="stylesheet" href="view/style.css">
</head>
<body>
	<nav>
		<ul>
			<li><a href="#" id="brand">Unsur Media</a></li>
			<li><a href="#" id="menu">About</a></li>
			<li><a href="#" id="menu">Contact</a></li>
			<li><a href="#" id="menu">Register</a></li>
			<li><a href="#" id="menu">Login</a></li>
		</ul>
	</nav>

	<header>
		<div class="container">
			<h1>Media Informasi Teknologi</h1>
			<p>Bersifat Global dan Detail</p>
		</div>
	</header>

footer.php

 	<footer>
		<div class="fotrs">
			<ul>
				<li><a href="#">Home</a></li>
				<li><a href="#">About</a></li>
				<li><a href="#">Contact</a></li>
			</ul>
		</div>
		<div class="fotrs">
			<div class="cr">
				© 2017 <a href="https://www.facebook.com/hausteknologi">Moch Fikri</a> | Made With ❤
			</div>
		</div>
		<div class="clear"></div>
	</footer>

</body>
</html>

index.php

 <?php require_once "view/header.php"; ?>

	<div class="container">
		<label for="">Nama</label><br>
		<input type="text" name="nama"><br><br>
		<label for="">Usernama</label><br>
		<input type="text" name="username"><br><br>
		<label for="">Password</label><br>
		<input type="password" name="password"><br><br>
		<label for="">Confirm Pass</label><br>
		<input type="password" name="confirm_pass"><br><br>
		<input type="submit" name="submit" value="Daftar">
	</div>

<?php require_once "view/footer.php"; ?>

style.css

 /*reset*/
*{
	margin: 0px;
	padding: 0px;
	font-family: sans-serif;
	font-weight: normal;
}
a{
	text-decoration: none;
}
li{
	list-style: none;
}
/*Style*/
.clear{
	clear: both;
}
nav{
	padding: 16px 17px 16px 100px;
	background: rgb(0, 128, 128);
}
nav ul li{
	margin: 0 10px;
	display: inline-block;
}
nav ul li #menu{
	opacity: .5;
	transition: .3s;
}
nav ul li #menu:hover{
	opacity: .8;
}
nav a{
	color: white;
}
nav ul li #brand{
	opacity: 1;
	margin-right: 10px;
	font-size: 1.3em;
}
header{
	background: rgb(52, 58, 64);
	padding: 75px 0;
	color: white;
}
header .container{
	padding-left: 80px;
}
header .container h1{
	font-size: 2.5em;
	margin-bottom: 10px;
}
header .container p{
	font-size: 1.25em;
}
footer{
	padding: 50px 0 50px 100px;
	border-top: solid gray 1px;
}
.fotrs{
	width: 50%;
	float: left;
}
.fotrs ul li{
	margin: 0 10px;
	display: inline-block;
}
.fotrs a{
	color: rgb(0, 123, 225);
	transition: .3s;
}
.fotrs a:hover{
	color: rgb(0, 65, 135);
}
.fotrs .cr{
	float: right;
	margin-right: 100px;
}
.container{
	width: 50%;
	margin: 0 auto;
}