PHP cannoy modify header information - headers already sent by ....

<?php 
require ‘../mysql_connect.php‘;
require(‘../model/functions.php‘);
include_once ‘../views/login.html.php‘;
 if ($_SERVER[‘REQUEST_METHOD‘] == ‘POST‘) {   // 处理表单
 	if (isset($_POST[‘login_submit‘])) {

        $role = $_POST[‘role‘];
 		$username = $_POST[‘username‘];
        $passwd = $_POST[‘p‘];

    if( user_login($pdo,$role,$username,$passwd) ){
        setcookie(‘userName‘,$name);              
        setcookie(‘password‘,$psw);    
        header("location: index.php");  
    }else{
        echo "<script>alert(‘输入信息错误，登录失败‘);</script>";
    }


 	}elseif (isset($_POST[‘get_password‘])) {

        $email = $_POST[‘email‘];
        user_register($pdo,$email);
 	}
}