Session study notes in php

Session refers to the time that a user spends browsing a website from entering the website to closing the browser. From the definition above

Session refers to the time that a user spends browsing a website from entering the website to closing the browser. From the above definition, we can see that Session is actually a specific concept of time.

When using PHP to apply a session, the session data is stored on the server, and the client information is identified by the sessionID sent from the client, and information is extracted.

The code for your own instance is as follows:

2. Session_start (); // start the session, which must be started in the session
3. $ _ SESSION ['name'] = "fangshan"; // sets the session, and the value of name is fangshan.
4. ?>
5. Next
6. (Save as session. php)
8. Session_start (); // start the session
9. If (isset ($ _ SESSION ['name']) // you can determine whether a SESSION exists.
10. {
11. Echo $ _ SESSION ['name'];
12. Echo "del session ";
13. }
14. Else
15. {
16. Echo "Session has not been setted ";
17. }
18. ?>
19. (Save as session2.php)
21. Session_start (); // start the session
22. Unset ($ _ SESSION ['name']); // deregister the session variable
23. Session_destroy (); // clear the session ID
24. Header ("Location: session2.php"); // jump back to the front page
25. ?>
26. (Save as deletesession. php)

Common session operations:

Write, read, register, and delete sessions.

Start of session

The start function of the session is session_start, and session_start is used to initialize the session variable. The syntax is as follows: session_start (); the return value is TRUE.

Write and read Sessions

In PHP, sessions are called and read through the predefined array $ _ session.

On the website page, assign values to the $ _ SESSION array on the registration page, and read the $ _ SESSION array on other pages.

Register the session on the page, for example, the following code:

2. Session_start ();
3. $ _ SESSION ['keyword'] = "php ";
4. ?>

For other sessions on the page, see the following code:

2. Session_start ();
3. Echo $ _ SESSION ['keyword'];
4. ?>

Run the command in sequence and the result is: php

Session detection and cancellation

Do you still remember isset and unset functions? These two functions implement session detection and cancellation respectively.

The isst function is used to check whether a session already exists. The syntax is as follows:

Bool isset ($ _ SESSION ['session _ name'])

For example, the following code:

2. Session_start ();
3. If (isset ($ _ SESSION ['keyword'])
4. Echo $ _ SESSION ['keyword'];
5. Else
6. Echo "www.phpfensi.com ";
7. ?>
8. // Result: php

The usset function is used to deregister a created session variable. Syntax:

Unset ($ _ SESSION ['session _ name'])

For example, the following code:

2. Session_start ();
3. Unset ($ _ SESSION ['keyword']);
4. If (isset ($ _ SESSION ['keyword'])
5. Echo $ _ SESSION ['keyword'];
6. Else
7. Echo "www.phpfensi.com ";
8. ?>
9. // Result: www.phpfensi.com

Php processes a total of 10 session functions. we will introduce several functions in detail.

1. session_start

Function: start a session or return an existing session.

Function prototype: boolean session_start (void );

Return value: Boolean

Function description: This function has no parameters and returns true. It is best to place this function first, and there cannot be any output before it, otherwise an alarm will be triggered, such as: Warning: cannot send session cache limiter-headers already sent (output started at/usr/local/apache/htdocs/cga/member/1.php: 2) in/usr/local/apache/htdocs/cga/member/1.php on line 3

2. session_register

Function: registers a new variable as a session variable.

Function prototype: boolean session_register (string name );

Return value: Boolean value.

Function description: This function adds a variable to the current SESSION in the global variable. the parameter name is the name of the variable to be added. if it succeeds, the logical value true is returned. You can use $ _ SESSION [name] or $ HTTP_SESSION_VARS [name] to set values or assign values.

3. session_is_registered

Function: checks whether a variable is registered as a session variable.

Function prototype: boobean session_is_registered (string name );

Return value: Boolean

Function description: This function checks whether a 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.

4. session_unregister

Function: Delete a registered variable.

Function prototype: boolean session_session_unregister (string name );

Return value: Boolean

Function description: This function deletes the variables in the global variables in the current session. The parameter name is the name of the variable to be deleted. if it is successful, true is returned.

5. Session_destroy

Function: ends the current session and clears all resources in the session.

Function prototype: boolean session destroy (void );

Return value: Boolean value.

Function description: This function ends the current session. this function has no parameters and returns true.

The functions described above will be used in the following sections, but there are also some functions related to the session:

6. session_encode

Function: sesssion information encoding

Function prototype: string session_encode (void );

Return value: string

Function description: the returned string contains the names and values of each variable in the global variable, in the form of a | s: 12: "it is a test"; c | s: 4: "lala"; a is the variable name s: 12 represents the value of variable a "it is a test the length is 12 variables are separated by semicolons.

7. session_decode

Function: decodes sesssion information.

Function prototype: boolean session_decode (string data)

Return value: Boolean

Function description: This function decodes session information. if the session information is successful, the logical value true is returned.

8. session_name

Function: Access the current session name.

Function prototype: boolean session_name (string [name]);

Return value: string

Function description: This function can obtain 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.

9. session_id

Function: Access the ID of the current session.

Function prototype: boolean session_id (string [id]);

Return value: string

Function description: This function can obtain or reset the ID number of the currently stored session. If no parameter id is specified, only the id of the current session is obtained. if a parameter is added, the id of the session is set to the new id.

10. session_unset

Function: delete all registered variables.

Function prototype: void session_unset (void)

Return value: Boolean

Function description: Unlike Session_destroy, this function does not end a session. Just like using the session_unregister function to cancel all session variables one by one.