高手 session 问题

[braqi2]

环境：linux+php+mysql,

session 配置上：
session
Session Support enabled
Registered save handlers files user

Directive Local Value Master Value
session.auto_start Off Off
session.bug_compat_42 Off Off
session.bug_compat_warn On On
session.cache_expire 180 180
session.cache_limiter nocache nocache
session.cookie_domain no value no value
session.cookie_lifetime 0 0
session.cookie_path /tmp /tmp
session.cookie_secure Off Off
session.entropy_file no value no value
session.entropy_length 0 0
session.gc_divisor 1000 1000
session.gc_maxlifetime 1440 1440
session.gc_probability 1 1
session.name PHPSESSID PHPSESSID
session.referer_check no value no value
session.save_handler files files
session.save_path /tmp /tmp
session.serialize_handler php php
session.use_cookies On On
session.use_only_cookies Off Off
session.use_trans_sid Off Off


相同的程序，在相同的linux+php+mysql 下，一个　session 正常，一个　session 失效。原因不能。
哪位大侠指点明津？
程序如下：
../../include/comm_sess.php
<?php
session_start();

if(empty($_COOKIE['fid'])){
session_start();
$sid=session_id();
setcookie("fid",$sid,time()+36000);
}else{
session_id($_COOKIE['fid']);
session_start();
}

?>
test.php
<?php
if(empty($_COOKIE['fid'])){
require "../../include/comm_sess.php";
$sid=session_id();
setcookie("fid",$sid,time()+36000);
}else{
session_id($_COOKIE['fid']);
require "../../include/comm_sess.php";
}

echo $_SESSION['lim_back1']="LUCADFA"; //此可以看到
?>
<?php
if(empty($_COOKIE['fid'])){
require "../../include/comm_sess.php";
$sid=session_id();
setcookie("fid",$sid,time()+36000);
}else{
session_id($_COOKIE['fid']);
require "../../include/comm_sess.php";
}
echo $_SESSION['lim_back1']; //这里没有
?>

[faisun]

另外两个文件没有 session_start();

[faisun]

echo $_SESSION['lim_back1']="LUCADFA"; //此可以看到
刚刚赋值当然可以看到啦

[braqi2]

有，在　include/comm_sess.php"; 里，并且我
test.php
<?php
session_start();
echo $_SESSION['lim_back1']="LUCADFA";
?>
tes1t.php
<?php
session_start();
echo $_SESSION['lim_back1']; //也得不到值
?>

[braqi2]

最奇的是，在另外一台相同配置的主机上就可以，所以我想可能是配置问题，大家帮忙看一下