php session_start()出错原因分析及解决方法

错误提示： Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent

原因：在session_start()之前如果有输出内容，会出错，

解决办法：在session_start()之前加上ob_start();

index.php 

<?php 
error_reporting(-1); 
ob_start();//不加会出错，无法写入session 
register_shutdown_function('close');   
echo 1; 
 session_start(); 
$_SESSION['password']='mima2ddddddddddddddda2'; 
function close() 
    { 
        if(session_id()!=='') 
            @session_write_close(); 
    } 
?> 
<a href="index2.php" >index2</a>

index2.Php

<?php 
error_reporting(-1); 
ob_start();//不加会出错，无法读取session 
?
echo 1; 
 session_start(); echo $_SESSION['password']; 
var_dump($_SESSION); 
?> 
<a href="index.php" >index</a>