What should I do if PHP cross-page delivery fails?

This article will introduce to you how to solve the problem of PHP cross-page delivery failure. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

This article mainly introduces the solution to the failure of PHP SESSION cross-page delivery. The article introduces it in detail through sample code, which has certain reference for everyone's study or work. Value, friends in need can refer to

Today I want to use a session to realize user login judgment, which can be regarded as an exploration of the previous session. I checked the information and the operating mechanism of the session is as follows:

session It is a session mechanism on the server side. When the client requests the server to create a session, the server will first detect whether the request contains a unique session ID. If so, it means that the server has already created a session for the user. Just search according to the session ID. The user's session is available for the user to use. If there is no session ID, the server will create a new session with a unique session ID for the user.

After the creation is completed, the sessionID will be returned to the client by the server and saved locally on the client.

The general mechanism for saving the session ID is Cookie, but since Cookies can be artificially prohibited, it is necessary to ensure that after Cookies are prohibited, the session can still be conducted through the session, usually through url rewriting,

The expression is www.fckfs.com ByOK3vjFD75aPnrF7C2HmdnV6QZcEbzWoWiBYEnLerjQ99zWpBng!-145788764. The other is as a query string appended to the end of the URL. The expression is http://..... /xxx?jsessionid=ByOK3vjFD75aPnrF7C2HmdnV6QZcE bzWoWiBYEnLerjQ99zWpBng!- 145788764 There is no difference between these two methods for users, but the way the server handles them during parsing is different. Using the first method is also helpful to distinguish session id information from normal program parameters.

In order to maintain state throughout the entire interaction process, this session id must be included at the end of each path that the client may request.

Another misunderstanding about session invalidation:

When talking about the session mechanism, we often hear the misunderstanding "As long as you close the browser, the session will disappear." In fact, you can imagine the example of a membership card. Unless the customer actively asks the store to cancel the card, the store will never delete the customer's information easily.

The same is true for sessions. Unless the program notifies the server to delete a session, the server will keep it. The program usually sends an instruction to delete the session when the user logs off.

However, the browser never actively notifies the server that it is about to close before closing, so the server has no chance to know that the browser has been closed. The reason for this illusion is that most session mechanisms use The session cookie is used to save the session id. After closing the browser, the session id disappears, and the original session cannot be found when connecting to the server again.

If the cookie set by the server is saved to the hard disk, or some method is used to rewrite the HTTP request header sent by the browser and send the original session id to the server, you can still find the original session id when you open the browser again. session.

It is precisely because closing the browser will not cause the session to be deleted, forcing the server to set an expiration time for the seesion. When the time since the client last used the session exceeds this expiration time, the server can consider the client The session will be deleted only when the client has stopped activities to save storage space.

Okay, let’s talk a lot of nonsense, let’s talk about the solution to session loss:

1. session_start(); should be placed at the top of the page as much as possible;

2. If session Autostart is not configured in php.ini, you must manually open the session before each session: session_start();

3. Session is a super global variable in php, followed by $_GET,$ _POST and $_SERVER are the same, so they must be capitalized when used:

$_SESSION['username']=$username;

4. Cross-page transfer example: a.php page passes $_SESSION['username'] to b.php:

a.php:

session_start();
$username=$_POST['username'];
$_SESSION['username']=$username;
?>

b.php:

session_start();
echo $_SESSION['username'];
?>

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