How to use php sessions? Session usage

How to use session
The session_start () function must be called before session-related operations ();

It is very easy to pay for the session, such:

Program code

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<? Php Session_start (); $ Name = "this is a Session example "; Session_Register ("Name"); // do not write it as Session_Register ("$ Name "); Echo $ _ SESSION ["Name"]; // After $ _ SESSION ["Name"] is "this is a Session example" ?>

After php4.2, you can directly pay the value for the session:

Program code

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<? PHP Session_Start (); $ _ SESSION ["name"] = "value "; ?>

You can cancel the session as follows:

Program code

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<? Php Session_start (); Session_unset (); Session_destroy (); ?>

There is a BUG in canceling a session variable above php4.2.

Read session

PHP's built-in $ _ SESSION variable allows you to easily access the set session variable.

Example:

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<? Php Session_start (); Echo "the registered user name is:". $ _ SESSION ["username"]; // The output user name is nostop. ?>

Check whether the variable is registered as a session variable

Session_is_registered

Syntax: boobean session_is_registered (string name );

This function can check whether the specified variable has been registered in the current session. The parameter name is the name of the variable to be checked. If the call succeeds, the logical value true is returned.

Example:

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<? Php Session_start (); If (! Session_is_registered ("gender") {// determines whether the current session variable is registered Session_register ("gender"); // registers the variable     } $ Gender = "female "; Echo $ _ SESSION ['gender']; // female ?>

Access the current session name

Session_name

Syntax: boolean session_name (string [name]);

This function can get or reset the name of the current session. If the parameter name is not set, the current session name is obtained. If the parameter is added, the session name is set to the parameter name.

Example:

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<? Php $ SessionName = session_name (); // Obtain the current Session name. The default value is PHPSESSID. $ SessionID = $ _ GET [$ sessionName]; // Obtain the Session ID. Session_id ($ sessionID); // use session_id () to set the Session ID. ?>

Access the current session ID

Session_id

Syntax: boolean session_id (string [id]);

This function can obtain or reset the ID number of the currently stored session. If there is no parameter id, only the id of the current session is obtained. If the parameter is added, the id of the session is set to the newly specified id.

Set the Session lifetime

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Setcookie: send an HTTP cookie to the client. <? Php Session_start // Save for one day $ LifeTime = 24*3600; Setcookie (session_name (), session_id (), time () + $ lifeTime ,"/"); ?>

Session_set_cookie_params: Set the Session lifetime. This function must be called before the session_start () function is called.
If the client uses IE 6.0, session_set_cookie_params (); the function sets the Cookie. Therefore, we need to manually call the setcookie function to create the cookie.

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// Save for one day <? Php $ LifeTime = 24*3600; Session_set_cookie_params ($ lifeTime ); Session_start (); $ _ Session ["admin"] = true; ?>

Set the Session file storage path

Session_save_path (): it must be called before the session_start () function is called.

The code is as follows:

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<? Php // Set a storage directory $ SavePath = "./session_save_dir /"; // Save for one day $ LifeTime = 24*3600; Session_save_path ($ savePath ); Session_set_cookie_params ($ lifeTime ); Session_start (); $ _ Session ["admin"] = true; ?> <? Php Session_start (); // start the Session $ Username = 'nostop '; Session_register ('Username'); // register a variable named username Echo 'registered User: '. $ _ SESSION ['username']; // registered User: nostop reads Session variables $ _ SESSION ['age'] = 23; // declare a variable named age and assign values Echo 'age: '. $ _ SESSION ['age']; // age: 23 Session_unregister ('Username'); // deregister the Session variable Echo $ _ SESSION ['username']; // null Echo $ _ SESSION ['age']; // 23 Unset ($ _ SESSION ['age']); // deregister the Session variable Echo 'registered User: '. $ _ SESSION ['username']; // null Echo 'age: '. $ _ SESSION ['age']; // null ?>

Note:

1: no output is allowed before Session_Start () is called. For example, the following is incorrect.

1 line
2 rows <? PHP
3 rows Session_Start (); // output already exists in the first row
4 rows .....
5 rows?>
========================================================== =

Tip 1:

If "... headers already sent..." appears, it means to output information to the browser before Session_Start.
It is normal to remove the output (this error will also occur in the COOKIE, the same reason for the error)

Tip 2:

If your Session_Start () is placed in a loop statement and it is difficult to determine where to output information to the browser, you can use the following method:
1 line <? PHP Ob_Start ();?>
... Here is your program ......

2: What is the error?

Warning: session_start (): open (/tmpsess_7d1_aa36b4c5ec13a5c1649cc2da23f, O_RDWR) failed :....
Because you have not specified the path for storing session files.

Solution:

(1) create a folder tmp on drive C
(2) open php. ini, find session. save_path, and change it to session. save_path = "c:/tmp"