Full session tutorial (2)_PHP tutorial

2. Implementation of session in PHP3 and 4

There is no such thing as session in php3, but we need it, what should we do? Don't worry, there are many people who have done this for you, the most famous of which is phplib. You can download it abroad, and you can download it from most domestic PHP sites. The first thing we need to do is get phplib and php3 together to make it work. In order to achieve this function, we need to install phplib first. Follow me, it's very easy (the following method is passed on win2000+php3.0.16+apache1.3.12+phplib7.2c+MySQL3.23.21 for win32) The most basic functions of PHPlib include user authentication, session management, permissions and database Abstraction.

How to use PHPlib to implement the session function?

1. First, unzip phplib. There is a directory called "php" inside. Copy this directory to the apache installation directory. Take the author's machine as an example: My apache is installed in the d:/apache directory. I copied the "php" directory above to d:a/pache, and copied the files and directories in the pages directory under phplib to Under d:/apache/htdocs, be careful not to include the directory itself. The phplib class library needs to be initialized according to the system. You can modify the local.inc file, which contains some basic parameters. You can modify it according to the actual situation of your machine. Change a program in the d:/apache/php/prepend.PHP3 file to look like this:

if (!isset($_PHPLIB) or !is_array($_PHPLIB)) {
$_PHPLIB["libdir"] = "d:/apache/php/"; //Change this to the path of the PHP directory under phplib
}

Then change the d:/apache/PHP/local.inc file as follows:

class DB_Example extends DB_Sql {
var $Host = "localhost";//The host name of your MySQL database
var $Database = "test"; //Database name
var $User = "root";//Database user name
var $Password = "";//Database user password
}

The last step is to execute the create_database.MySQL file in the stuff directory in the unpacked phplib directory to generate the initial table. Let’s explain how phplib works. Every page that uses phplib must first find the class library files necessary to run phplib. We can set the auto_prepend variable in php3.ini to support it. The phplib distribution package contains a prepend.php3 file. After specifying "d:/apache/php/prepend.php3" (with quotes) for auto_prepend, each page will automatically include the phplib class library. We can also add the directory where the phplib class library is located to the include variable so that these can be found. File, of course, the easiest way is to specify the absolute path of PHPlib. This is not a good idea, the portability is too poor!

Second step, in every page using phplib, you must first call the page_open function for initialization. This tells PHPlib that you will need to save state now or in the future. A typical
An example of page_open is as follows:

page_open(array("sess" => "Example_session"));
?>

Array variables (sess) are used to initialize some state saving objects. Note: phplib built-in names (sess) must be used. These built-in names are defined by you in local.ini. The page_open function must output the page content to the browser. was called before. The PHP3 script should end with page_close(), which will write the relevant status data back to the database. If you forget, you should be able to think of the result, haha, all your variables are lost, don’t blame me for not telling you. ...

Because phplib uses Cookies to save state information, the page_open() function must be called before the page content is output to the browser. The page content here can be any HTML information or blank lines. If you find the error "Oops - SetCookie called after header has been sent", this indicates what was output to the browser before page_open(). You should pay special attention to blank lines, because they are very difficult to find. Typical errors are in the tags Blank lines are output between. You should check whether the local.inc and prepend.PHP3 files contain blank lines. This is also a very error-prone place. In order to reduce the possibility of errors, we can write the initialization program like this:
page_open(array("sess" => "Example_session"));
?>

.....

The third step is specific use.
When a user visits the website, the user's session starts immediately. If the user's browser supports cookies, a session ID will be created and placed in the cookie. This unique ID is randomly generated by PHP3, and then used The random seed string has been md5 encrypted. The cookie here should be called a session cookie, because this cookie will not be written to the user's hard drive. When a session ends, the cookie will also be completed. If the user's browser does not support cookies, then the session ID will be put into the URL chain. Because it is encrypted, it is useless to steal it. The session ID stores user-related information, such as the user has been authenticated, authentication expiration time, user permissions, and other information you may need for our convenience. Session is actually the process of a user session. Session is not just used to track user registration. In fact, it can also be used in other situations. You can use it to store any information you want to store. This information can be sent to the pages that the user subsequently visits. Useful, of course, the premise is that those pages use PHPLIB. The method is very simple. After registering a variable, you can use it in subsequent pages until the session ends. Method:
register( "variable_name"); ?>

Note that the variable_name here is not the variable value, but the variable name. You can specify the variable name first and then assign the value. You can change the value of a variable in a page, and subsequent pages will get the changed value when accessing the variable. The types of variables are diverse and can be a string, a number, or an array. To illustrate with an example:

First page:
page_open(array("sess" => "Example_session"));
$sess->register( "first"); //Note that there is no need to add $ before the variable name
if (iset($firstname)) {
$first = $firstname;
}
.....
page_close();
?>

Second page:
page_open();//Start session

echo $first;//See the effect

page_close();//Save status information
?>

After registering a variable, when the page finally calls the page_close() function, each session variable will be written back to the database. If you forget to call the page_close() function, the variables will not be written back to the database, and unpredictable consequences will occur. When the variable is used and you no longer need it, you can call the following function to delete the variable:

page_open(array("sess" => "Example_session"));
...
$sess->unregister( "variable_name");
...
page_close();
?>

PHPLIB 7.0 uses a storage structure that allows you to store session data in a database, shared memory or LDAP. PHPLIB uses database classes, which gives you more choices. You can choose Oracle8, MySQL, postgresql and other databases to save status information.

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