SESSION management in PHP4_PHP tutorial

The most eye-catching new feature of PHP4 is the SESSION management function. When others visit your site, you can save variables to the SESSION object to achieve many new functions.
What is SESSION
If you are still unclear, let me first explain what a SESSION is. A SESSION starts when someone visits your website and ends when he leaves the website. Of course, you can also terminate it in the program. Basically, COOKIE is related to browsing Associated with the server, some resources on the server are used to save SESSION variables. By default, PHP4 uses files to save these variables. Of course, in theory, it can also be saved in a database or shared memory.
All web pages that use the SESSION feature of PHP4 must call the session_start() function to let the PHP4 engine load SESSION-related information into memory. The session_start function will try to find the SESSION ID from COOKIE or the parameters of the current HTTP request. If not found, a new SESSION object will be created.
What is a SESSION variable?
The SESSION variable is actually an ordinary global variable. When registered (declared) as a SESSION variable, all PHP4 All web pages with the SESSION function can access its value. To register a variable as a SESSION variable, just assign a value to the variable first, and then call session_register("variable name"). In subsequent web pages that use the SESSION function (through session_start) , the variable "variable name" does not need to be re-registered as a SESSION variable. It is just like an ordinary variable, and its value is what was assigned to it previously. If the value of this variable is changed in the program, it will be automatically re-registered and saved. , and can be used normally in its subsequent web pages.
So, what can it do?
Good question! There are many ways to use SESSION management and SESSION variables. Here, I will give an example to illustrate. If you are building a virtual community site, you may want to track the currently verified user name and how many new messages he has. In order to reduce the load on the database, you need to use other methods to save this information. There are two methods :
Use three COOKIES
authenticatied_user - the current verified user name
num_message - how many new messages he has

expire_time - the expiration time limit of COOKIE
Use SESSION, register three SESSION variable
The first method has great security risks. Others can forge COOKIE and then use another account to access the system. Besides, all information is implemented through the HEADER() function, which is quite troublesome. In addition, when If the user's browser refuses to accept one of the COOKIES, the entire data will be incomplete.
With SESSION, only one COOKIE can save all the information. The security is also better.
Disadvantages
Using any server-side scripting language, SESSION can provide a very free, flexible and powerful function. But SESSION in PHP4 has some limitations: -Objects themselves cannot be saved in SESSION -Saved in SESSION The data efficiency is not very high because PHP4 uses files to save SESSION information.

http://www.bkjia.com/PHPjc/532065.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/532065.htmlTechArticleThe most eye-catching new feature of PHP4 is the SESSION management function. When others visit your site, You can save variables into the SESSION object to achieve many new functions. What is...