What should I do if php cannot pass session?

Solution to the problem that php cannot pass session: 1. Enable cookies in the client; 2. Check browser issues and access cookies; 3. Enable session.use_trans_sid in php.ini.

##The operating environment of this article: windows7 system, PHP7.1 version, DELL G3 computer

Solution to the problem that SESSION cannot be passed across pages in PHP

Friends who have used SESSION in PHP may encounter such a problem, the SESSION variable cannot be passed across pages. This troubled me for several days, and I finally thought about and solved the problem by looking up information. I think the reasons for this problem are as follows:

1. Cookies are disabled on the client
2. There is a problem with the browser and cookies cannot be accessed temporarily
3. The session in php.ini. use_trans_sid = 0 or the --enable-trans-sid option was not turned on during compilation

Why is this happening? Let me explain below:

Session is stored on the server side (session is stored as a file by default). According to the session id provided by the client, the user's file is obtained and the value of the variable is obtained. The session id can use the client's cookie. Or the Query_String of the Http1.1 protocol (the part after the "?" of the accessed URL) is sent to the server, and then the server reads the Session directory. In other words, session id is the ID card for obtaining the session variable stored on the service. When the code session_start(); is run, a session file is generated on the server, and a session id uniquely corresponding to it is generated. The session variable is defined to be stored in the session file just generated in a certain form. Through the session id, the defined variables can be retrieved. After crossing the page, in order to use the session, you must execute session_start() again; another session file will be generated, and the corresponding session id will be generated accordingly. Using this session id, you cannot retrieve the first session file mentioned earlier. variable in, because this session id is not the "key" to open it. If you add the code session_id($session id); before session_start();, a new session file will not be generated, and the session file corresponding to this id will be read directly.

The session in PHP uses the client's cookie to save the session id by default, so when there is a problem with the client's cookie, it will affect the session. It must be noted that session does not necessarily have to rely on cookies, which is also the brilliance of session compared to cookies. When the client's cookies are disabled or there is a problem, PHP will automatically attach the session id to the URL, so that the session variable can be used across pages through the session id. But this attachment also has certain conditions, namely "session.use_trans_sid = 1 in php.ini or the --enable-trans-sid option is turned on during compilation".

Understanding the above principles, now let’s put aside cookies and use sessions. There are three main ways:

1. Set session.use_trans_sid = 1 in php.ini or open it during compilation. The --enable-trans-sid option is added to allow PHP to automatically pass session ids across pages.

2. Manually pass the value through the URL and pass the session id through the hidden form.
3. Save session_id in a file, database, etc., and call it manually during the cross-page process.

Let’s illustrate with an example:

s1.phps2.php

## php

session_start ();                                    $_SESSION [ ' var1 ' ] = " People's Republic of China " ; ;
$url = " Next page " ;
echo ​ $url ;                                    ?>

php
session_start ();                                             echo ​ " The value of the passed session variable var1 is: " . $_SESSION [ ' var1 ' ];
?>

Run the above code. If the client cookie is normal, you should be able to get the result "People's Republic of China".

Now if you manually close the cookie on the client and run it again, you may not get the result. If you can't get the result, then "set session.use_trans_sid = 1 in php.ini or turn on the --enable-trans-sid option when compiling", and you will get the result "People's Republic of China"

This This is the approach 1 mentioned above.

Let’s talk about approach 2:

The modified code is as follows:

s1.php

php

session_start ();                                           $_SESSION [ ' var1 ' ] = " People's Republic of China " ; ; $sn ​ = ​ session_id ();                                        $url = " Next page " ;
echo ​ $url ;                                         ?>


s2.php method 3: login.html

  php
  session_id   (   $_GET   [   '   s   '   ]);                              
  session_start   ();                                     
  echo       "   传递的session变量var1的值为：   "   .   $_SESSION   [   '   var1   '   ]; 
  ?>  

 

       
                

      Login     title   >                                                   
   
    head   >                                                                
     请登录：                                                 
 

   action   =   "   mylogin1.php   "   >                                                 
用户名   :                              
口　令   :                          
                                       
    form   >                                                                
    body   >                                                                
    html   >      

 

mylogin1.php

<?   php

   $name   =   $_POST   [   &#39;   name   &#39;   ];
   $pass   =   $_POST   [   &#39;   pass   &#39;   ];
   if   (   !   $name       ||       !   $pass   ) {
   echo       "   用户名或密码为空，请<a href="login.html">重新登录</a>   "   ;
   die   ();
}
   if    (   !   (   $name   ==   "   laogong   "       &&       $pass   ==   "   123   "   )) {
   echo       "   用户名或密码不正确，请<a href="login.html">重新登录</a>   "   ;
   die   ();
}
   //   注册用户  
   ob_start   ();
   session_start   ();
   $_SESSION   [   &#39;   user   &#39;   ]   =       $name   ;
   $psid   =   session_id   ();
   $fp   =   fopen   (   "   e:/tmp/phpsid.txt   "   ,   "   w+   "   );
   fwrite   (   $fp   ,   $psid   );
   fclose   (   $fp   );
   //   身份验证成功，进行相关操作  
   echo       "   已登录<br>   "   ;
   echo       "   <a href="mylogin2.php">下一页</a>   "   ;

   ?>

mylogin2.php

php
$fp = fopen ( " e:/tmp/phpsid.txt " , " r " );
$sid = fread ( $fp , 1024 );
fclose ( $fp );
session_id ( $sid );
session_start ();
if ( isset ( $_SESSION [ ' user ' ]) && ​ $_SESSION [ ' user ' ] = " laogong " ) {
echo ​ " Has logged! " ;
}
else {
// Successfully log in to perform related operations
echo ​ " Not logged in, no access rights " ;
echo ​ " Pleaselog in to browse " ;
Die ();
}

?>

Please also turn off the cookie test. Username: laogong Password: 123 This is to save the session id through a file. The file is: e:/tmp/phpsid.txt. Please decide the file name or path according to your own system. .

As for the database method, I will not give an example, it is similar to the file method.

To summarize, the above methods have one thing in common, which is to get the session id on the previous page, and then find a way to pass it to the next page. Add the code session_id (pass it) before the session_start(); code on the next page. Session id that came over);

Recommended study: "PHP Video Tutorial"

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