Bootstrap下拉列表没有工作包括标题php

I have two pages home.php and header.php now the header file has the the top navigation bar that is to be included in the home.php page.I used a bootstrap drop down in header.php and it is working fine but when I am including header.php in home.php the nav bar is appearing perfect but the dropdown is not working so please help.Here are my codes
header.php

<?php
if(!isset($_SESSION)) 
    { 
        session_start(); 
    } 
if(isset($_SESSION['user']))
{
    $user=$_SESSION['user'];
}
?>
<!DOCTYPE HTML>
<html>
<head>
    <link rel="SHORTCUT ICON" href="images/icon/logo.ico">
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" media="all" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
    </head>
<body>
<?php
require_once("dbconnect.php");
$query="SELECT * FROM user WHERE email='{$user}'";
$result=mysqli_query($con,$query);
$row=mysqli_fetch_array($result);
$name=ucfirst($row[1]);
?>
    <!--Navigation bar-->
    <div class="navi">
    <nav class="navbar navbar-default navbar-fixed-top navbar-inverse">
        <div class="container-fluid">
            <div class="navbar-header">
                <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#myNavbar">
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span> 
                </button>
                <div class="navbar-brand">&nbsp;&nbsp;&nbsp;Rankethon</div>
                <form role="search" class="navbar-form navbar-left">
            <div class="input-group">
                                    <input type="text" class="form-control" placeholder="Search for friends.." size="50" id="query" name="search" value="">
                                        <div class="input-group-btn">
                                    <button type="submit" class="btn btn-success"><span class="glyphicon glyphicon-search"></span></button>
                                    </div>
                                </div>
            </form>
            </div>
            <div class="collapse navbar-collapse" id="myNavbar">
                <ul class="nav navbar-nav navbar-right">
                    <li><a href="#"><span class="glyphicon glyphicon-home" aria-hidden="true"></span><b> Home</b></a></li>
                    <li><a href="#"><span class="glyphicon glyphicon-user" aria-hidden="true"></span><?php echo "<b>$name</b>";?></a></li>
                    <li><a href="#"><span class="glyphicon glyphicon-tags" aria-hidden="true"></span><b> Noifications</b></a></li>
                    <li class="dropdown">
                    <a id="dLabel" data-target="#" href="#" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">
                    <span class="glyphicon glyphicon-cog" aria-hidden="true"></span>
                    <b>Account</b>
                    <span class="caret"></span>
                    <ul class="dropdown-menu dropdown-menu-right" aria-labelledby="dLabel">
                    <li><a href="#" style="text-align:center"><b>Settings</b></a></li>
                    <li><a href="#" style="text-align:center"><b>About Us</b></a></li>
                    <li role="separator" class="divider"></li>
                    <li><a href="logout.php" style="text-align:center"><strong>Logout</strong></a></li>
                    </ul>
                    </a>
                    </li>
        </div>
    </nav>
</body>
</html>

home.php

<?php
if(!isset($_SESSION)) 
    { 
        session_start(); 
    } 
if(!(isset($_SESSION['user'])))
{
    header('location:logout.php');
}
?>
<!DOCTYPE HTML>
<html>
<head>
    <link rel="SHORTCUT ICON" href="images/icon/logo.ico">
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" media="all" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
    <link rel="stylesheet" type="text/css" href="css/style.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
    <script> $(document).ready(function () { $('.dropdown-toggle').dropdown(); }); </script>
</head>
<body>
<?php
include("header.php");
?>
</body>
</html>

</div>

this happens because you markup is invalid, because you embed the html tag two times.

Regards, Patrick