PHP shares SESSION data with multiple servers

PHP allows multiple servers to share SESSION data. 1. websites with a slightly larger problem generally have several servers. each server runs modules with different functions and uses different second-level domain names, for a website with a strong integrity, the user system is unified, that is, a set of user names and passwords can be used to log on to all modules of the website. Each server shares user data in PHP to achieve multi-server sharing SESSION data

I. problem origin
Websites with a slightly larger size usually have several servers. each server runs modules with different functions and uses different second-level domain names. The User System of a website with a strong integrity is unified, that is, a set
The user name and password can be used in all modules of the website. Each server shares user data easily. you only need to add a database server on the backend.
Access user data. However, there is still a problem, that is, after logging on to the server, the user still needs to log on again when entering another module of the server.
The question of how to implement SESSION data sharing between servers is mapped to the technology.
II. working principles of PHP sessions
Before solving the problem, let's take a look at the working principles of the php session. When a client (such as a browser) logs on to a website, the Accessed PHP page can be used
Session_start () opens the SESSION, which generates the unique session id of the client.
Session_id () get/set ). The session id can be retained on the client in two ways, so that the PHP program can obtain
Session id. one is to automatically add the session id to the get url or POST form. by default, the variable name is
PHPSESSID; the other is to save the session id in the COOKIE through the COOKIE. by default, the COOKIE name is
PHPSESSID. Here we mainly describe the COOKIE method, because it is widely used.
Where can SESSION data be stored? Of course, it is on the server side, but not stored in the memory, but saved in a file or database. By default
The SESSION is saved as files (session. save_handler = files), that is, the SESSION is saved as a read/write file.
The SESSION file is stored in the directory specified by session. save_path. the file name is prefixed with sess _, followed by SESSION
ID, for example, sess_cda-65af28a8b14c0fe11afe3b59b51b. The data in the file is the serialized SESSION.
Data. If the traffic volume is large, many SESSION files may be generated. you can set a hierarchical directory for SESSION
The file storage efficiency will be improved a lot. the setting method is: session. save_path = "N;/save_path", N is the hierarchical level, save_path
Is the start directory. When writing SESSION data, PHP will get the SESSION_ID of the client, and then according to the session id to the specified
Find the corresponding SESSION file in the SESSION file storage directory. if the file does not exist, create the file and write the data into the file after serialization. Read SESSION
Data is similar to the operation process, and the read data needs to be deserialized to generate the corresponding SESSION variable.
III. main obstacles and solutions to multi-server SESSION sharing
By understanding the working principle of the SESSION, we can find that by default, each server generates a SESSION for the same client separately.
ID. for example, for the same user browser, the session id generated by server A is 30de1e9de3192ba6ce2992d27a1b6a0a, while
Server B generates c000065af28a8b14c0fe11afe3b59b51b. In addition, PHP SESSION
Data is stored in the file system of the current server. As shown in:

After confirming the problem, you can start to solve it. To share SESSION data, you must achieve two goals: one is generated by each server on the same client.
The session id must be the same and can be passed through the same COOKIE. that is to say, each server must be able to read
COOKIE; the other is the storage mode/location of SESSION data, which must be accessible to all servers. [Color = "green"] Simply put, a multi-server shares the session id of the client, and the SESSION data of the server must also be shared.
The implementation of the first target is actually very simple. you only need to set the COOKIE domain. by default, the COOKIE domain is the domain name/IP address of the current server, if the domain is different, the cookies set by each server cannot access each other, for example?
Www.aaa.com
The server cannot read or write?
Www.bbb.com
The COOKIE set by the server. The server of the same website has its own particularity, that is, they belong to the same level-1 domain, such as aaa.infor96.com and?
Www.infor96.com
All belong to the domain .infor96.com, so we can set the COOKIE domain to .infor96.com, so that aaa.infor96.com and www.infor96.com can access this COOKIE. The setting method in PHP code is as follows:
('Session. cookie_domain ',' .infor96.com ');
?>
In this way, each server shares the same client session id.
The implementation of the second target can use the file sharing method, such as the NFS method, but the settings and operations are somewhat complicated. We can refer to the previous method of unified user system, that is, using a database to save SESSION data, so that each server can easily access the same data source and obtain the same SESSION data.
The solution is shown in:

IV. code implementation
First, create a data table. the MySQL SQL statement is as follows:
? ? Create table 'sess '(
? ??? 'Sskey' varchar (32) not null default '',
? ?? ? 'Expiry' bigint (20) not null default '0 ',
? ?? ? 'Data' longtext not null,
? ?? ? Primary key ?? ('Sskey '),
? ?? ? KEY 'expiry' ('expiry ')
? ? ) ENGINE = MyISAM default charset = utf8 COLLATE = utf8_unicode_ci
Sesskey is the session id, expiry is the SESSION expiration time, and data is used to save SESSION data.
By default, SESSION data is saved as files. to save data as a database, you must redefine the processing functions of each SESSION operation. PHP provides
Session_set_save_handle ()
Function. you can use this function to customize the SESSION processing process. of course, you must first change session. save_handler to user, which can be set in PHP:
('User ');
?>
Next we will focus on the session_set_save_handle () function, which has six parameters:
Session_set_save_handler (string open, string close, string read, string write, string destroy, string gc)
Each parameter is the function name of each operation. these operations are: open, close, read, write, destroy, and garbage collection. The PHP manual contains detailed examples. here we use the OO method to implement these operations. the detailed code is as follows:
('My _ SESS_TIME, 3600 );? ? // SESSION survival duration
// Class definition
Class My_Sess
{
? ? Function init ()
? ? {
? ?? ??? $ Domain = '.infor96.com ';
? ?? ??? // Do not use the GET/POST variable method
? ?? ??? Ini_set ('session. use_trans_sid ',? ? 0 );
? ?? ??? // Set the maximum time to live for garbage collection
? ?? ??? Ini_set ('session. gc_maxlifetime ',? ? MY_SESS_TIME );
? ?? ??? // Use cookies to save SESSION IDs
? ?? ??? Ini_set ('session. use_cookies ',? ?? ? 1 );
? ?? ??? Ini_set ('session. cookie_path ',? ?? ? '/');
? ?? ??? // Multiple hosts share the COOKIE that saves the SESSION ID
? ?? ??? Ini_set ('session. cookie_domain ',? ? $ Domain );
? ?? ??? // Set session. save_handler to user instead of the default files
? ?? ??? Session_module_name ('user ');
? ?? ??? // Define the method name for each SESSION operation:
? ?? ??? Session_set_save_handler (
? ?? ?? ?? ? Array ('My _ sess', 'open '),? ? // Corresponds to the static method My_Sess: open (), the same below.
? ?? ?? ?? ? Array ('My _ sess', 'close '),
? ?? ?? ?? ? Array ('My _ sess', 'read '),
? ?? ?? ?? ? Array ('My _ sess', 'write '),
? ?? ?? ?? ? Array ('My _ sess', 'deststroy '),
? ?? ?? ?? ? Array ('My _ sess', 'gc ')
? ?? ???);
? ? }? ? // End function
? ? Function open ($ save_path, $ session_name ){
? ?? ??? Return true;
? ? }? ? // End function
? ? Function close (){
? ?? ??? Global $ MY_SESS_CONN;
? ?? ??? If ($ MY_SESS_CONN ){? ? // Close the database connection
? ?? ?? ?? ? $ MY_SESS_CONN-> Close ();
? ?? ???}
? ?? ??? Return true;
? ? }? ? // End function
? ? Function read ($ sesskey ){
? ?? ??? Global $ MY_SESS_CONN;
? ?? ??? $ SQL = 'SELECT data FROM sess WHERE sesskey = '. $ MY_SESS_CONN-> qstr ($ sesskey).' AND expiry> = '. time ();
? ?? ??? $ Rs = & $ MY_SESS_CONN-> Execute ($ SQL );
? ?? ??? If ($ rs ){
? ?? ?? ?? ? If ($ rs-> EOF ){
? ?? ?? ?? ?? ? Return ";
? ?? ?? ?? ?} Else {? ? // Read the SESSION data corresponding to the SESSION ID
? ?? ?? ?? ?? ? $ V = $ rs-> fields [0];
? ?? ?? ?? ?? ? $ Rs-> Close ();
? ?? ?? ?? ?? ? Return $ v;
? ?? ?? ?? ?}? ? // End if
? ?? ???}? ? // End if
? ?? ??? Return ";
? ? }? ? // End function
? ? Function write ($ sesskey, $ data ){
? ?? ??? Global $ MY_SESS_CONN;
? ?? ???
? ?? ??? $ Qkey = $ MY_SESS_CONN-> qstr ($ sesskey );
? ?? ??? $ Expiry = time () + My_SESS_TIME ;? ? // Set the Expiration Time
? ?? ???
? ?? ??? // Write the SESSION
? ?? ??? $ Arr = array (
? ?? ?? ?? ? 'Sskey' => $ qkey,
? ?? ?? ?? ? 'Expiry '?? =>$ Expiry,
? ?? ?? ?? ? 'Data '? ? => $ Data );
? ?? ??? $ MY_SESS_CONN-> Replace ('sess', $ arr, 'sesskey', $ autoQuote = true );
? ?? ??? Return true;
? ? }? ? // End function
? ? Function destroy ($ sesskey ){
? ?? ??? Global $ MY_SESS_CONN;
? ?? ??? $ SQL = 'delete FROM sess WHERE sesskey = '. $ MY_SESS_CONN-> qstr ($ sesskey );
? ?? ??? $ Rs = & $ MY_SESS_CONN-> Execute ($ SQL );
? ?? ??? Return true;
? ? }? ? // End function
? ? Function gc ($ maxlifetime = null ){
? ?? ??? Global $ MY_SESS_CONN;
? ?? ??? $ SQL = 'delete FROM sess WHERE expiry. time ();
? ?? ??? $ MY_SESS_CONN-> Execute ($ SQL );
? ?? ??? // Due to frequent deletion operations on the table sess, fragments are easily generated,
? ?? ??? // Optimize the table in garbage collection.
? ?? ??? $ SQL = 'optimize TABLE sess ';
? ?? ??? $ MY_SESS_CONN-> Execute ($ SQL );
? ?? ??? Return true;
? ? }? ? // End function
}? ? ///:~
// Use ADOdb as the database abstraction layer.
Require_once ('adodb/adodb. inc. php ');
// Database configuration items, which can be placed in the configuration file (for example, config. inc. php ).
$ Db_type = 'mysql ';
$ Db_host = '192. 168.212.1 ';
$ Db_user = 'sess _ user ';
$ Db_pass = 'sess _ pass ';
$ Db_name = 'sess _ db ';
// Create a database connection. this is a global variable.
$ GLOBALS ['My _ sess_conn'] = & ADONewConnection ($ db_type );
$ GLOBALS ['My _ sess_conn']-> Connect ($ db_host, $ db_user, $ db_pass, $ db_name );
// Initialize the SESSION settings, which must be run before session_start !!
My_Sess: init ();
?>
V. legacy issues
If the website has a large access volume, the SESSION reads and writes the database frequently, which significantly reduces the efficiency. Considering SESSION
Generally, the data is not very large. you can try to write a multi-threaded program in C/Java, use the HASH table to save SESSION data, and use the socket
Communication for data read/write, so that SESSION
It is stored in the memory, and the read/write speed should be much faster. In addition, server load balancing can be used to share the server load. But these are just some of my own ideas and assumptions, and I have never practiced them?