可能重复：
PHP 已发送标头
我是面向对象PHP的新手。这段代码在函数php中运行良好，但在OOP php中会出现一些错误。
当我打开index.php时，错误消息如下所示，但所有其他代码都运行良好：：
Warning: session_start() [function.session-start]: Cannot send session cookie - headers
already sent by (output started at
E:'XAMPP'xampp'htdocs'photo_gallery_new'public'layout'header.php:14) in
E:'XAMPP'xampp'htdocs'photo_gallery_new'Includes'session.php on line 15
Warning: session_start() [function.session-start]: Cannot send session cache limiter -
headers already sent (output started at
E:'XAMPP'xampp'htdocs'photo_gallery_new'public'layout'header.php:14) in
E:'XAMPP'xampp'htdocs'photo_gallery_new'Includes'session.php on line 15
代码：：
index.php
<?php include ("../public/layout/header.php"); ?> // for design header
<h2> Menu </h2>
<?php
require_once ("../Includes/initiate.php"); // it makes error
//require_once ("../Includes/user.php"); // it works
//require_once ("../Includes/database_object.php"); // it makes error
echo $user->full_name();
echo "<hr />";
?>
</div>
<?php include ("../public/layout/footer.php"); ?> // design for footer
user.php
<?php
require_once ("database.php");
class USER extends databaseObject { // it makes error
//class USER { // but it works
public $id; public $username; public $password; public $firstName;
public $lastName;
// user authenticate
public static function authenticate( $username="", $password="" ) { ... }
public function full_name() {..... } // find full name
// common database action
public static function record_all_user() { ... } // find all user
public static function record_by_id($id=0) {.....} // find specific user
public static function record_by_sql($sql="") { ...... } // check sql
?>
header.php
<html>
<head>
<title> Photo Gallery </title>
<link href="stylesheet/main.css" media="all" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="header">
<h1> PHOTO GALLERY </h1>
</div>
<div id="main">
session.php
<?php
class Session {
private $logged_in = FALSE;
public $user_id;
function __construct() {
session_start();
$this->check_login();
.............................
}
public function is_logged_in() {....} // check loged in
public function login($user) { ..... }
public function logout() {
unset($_SESSION['user_id']);
unset($this->user_id);
$this->logged_in = FALSE;
}
private function check_login() {... .} // check login
}
$session = new Session();
?>
initiate.php
<?php
require_once ("Config.php");
require_once ("Functions.php");
require_once ("session.php");
require_once ("Database.php");
require_once ("database_object.php"); // this makes error
require_once ("user.php");
?>
database_object.php
<?php
require_once ("database.php");
class databaseObject {
}
$newClass = new databaseObject();
?>
您不能包含在调用session_start();之前直接发送给用户的任何东西这包括空白、html等等。
请确保您的第一个<?php之前没有任何空白。请确保在调用session_start的之后包含标头。这应该能解决问题。
尝试更改require语句的顺序：
<?php
require_once ("session.php");
require_once ("Config.php");
require_once ("Functions.php");
require_once ("Database.php");
require_once ("database_object.php"); // this makes error
require_once ("user.php");
?>
php会话需要在将任何内容发送到浏览器之前启动。
检查，您可能有echo、print在会话创建之前提供输出
在index.php文件中，您正在向浏览器输出字符：
<?php include ("../public/layout/header.php"); ?> // for design header
<h2> Menu </h2> <----- this line
<?php
require_once ("../Includes/initiate.php"); // it makes error
您必须将require_one文件移到这一行上方，或者缓冲输出，直到发送完所有标头。
在调用session_start()之前不应产生任何输出。
在您的index.php中，包括../Includes/initiate.php。在这个文件中，包含了session.php，它在构造函数中调用session_start()。这会产生一个错误，因为您已经在index.php中生成了包含header.php的输出。