关于session_start()的问题
我的系统流程是这样的：首先管理员输入用户名和密码登录后，系统会直接跳转到result.php。而我在result.php中写入这么一段，以防止用户在地址栏直接输入result.php访问。
<?php include "conn.php"; include "admin_header.php"; session_start(); if($_SESSION["admin_name"]==""&&$_SESSION["admin_pass"]==""){ session_write_close(); header("Location:index.php"); }?>但是登录后系统提示： A session had already been started - ignoring session_start() on line 5
回复讨论(解决方案)
php5.4？
你程序中多次执行了 session_start()
包含的两个文件中已经有了session_start()
php5.4？
你程序中多次执行了 session_start() wamp2.2的，我也不知道我的php是什么版本的。我的admin_header.php里也有这么一段，是不是跟这个有关系？但是如果我把这个文件里的这段去掉的话，用户就可以直接输入文件名访问了呀！
不用整段去掉，判断一下是否start了，否再执行 session_start() 不就行了
另一个问题（跟你说的问题无关）， session_start() 前面怎么有空行呢？
不用整段去掉，判断一下是否start了，否再执行 session_start() 不就行了
另一个问题（跟你说的问题无关）， session_start() 前面怎么有空行呢？ 我自己加的空行，为了跟前两个调用的文件区分开，是不是书写格式错误，那我改回来。
另一个问题，判断是否start的语句是怎么样的？
对了，我还有一个login.php是在admin.php文件里输入用户名和密码后在login.php里验证是否正确的，正确以后就跳到result.php。这个login.php里有没有需要修改的？
<?php //用户身份验证session_start();include "conn.php";include "header.php";extract($_POST); if ($admin_name!=$admin || $admin_pass!=$pass_admin){ echo"<p align=\"center\"><font color=\"#FF0000\"><b><big>请确认用户名和密码是否正确</big></b></font></p>"; echo("<HTML><META http-equiv=\"refresh\" content =\"1;url=admin.php\"></HTML>"); exit;}else{ $_SESSION["admin_name"]=$admin_name; $_SESSION["admin_pass"]=$admin_pass; echo("<HTML><META http-equiv=\"refresh\" content =\"0;url=result.php\"></HTML>"); exit;}include "foot.php";?> 你include进去的里面有session_start()了，两次开启就会出现你这种情况，可以在你include进去的代码里面用完之后关闭session，或者这个里面代码里面去掉session_start()。
这样可以判断session是否开启
if(!isset($_SESSION)){
session_start();
}
你include进去的里面有session_start()了，两次开启就会出现你这种情况，可以在你include进去的代码里面用完之后关闭session，或者这个里面代码里面去掉session_start()。
这样可以判断session是否开启
if(!isset($_SESSION)){
session_start();
} 那如果我还想在跳到系统首页之前加一句“用户非法登录”，应该怎么加呢？
你include进去的里面有session_start()了，两次开启就会出现你这种情况，可以在你include进去的代码里面用完之后关闭session，或者这个里面代码里面去掉session_start()。
这样可以判断session是否开启
if(!isset($_SESSION)){
session_start();
} 那如果我还想在跳到系统首页之前加一句“用户非法登录”，应该怎么加呢？ 在系统首页对是否正常登陆的这个session进行判断，比如正常登陆让这个session为1，不正常为0，判断到为0就alert一个“用户非法登录”就可以了
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