User status Management (session support) is PHP 4.0 a new feature that has been expected for a long time. In the era of PHP 3.0, programmers had to use a library that other people wrote to implement state management functions, or simply give up on this feature. The lack of state management functionality is actually one of the most disappointing parts of PHP 3.0. However, now that the situation has changed, from the early beta version of PHP 4.0, User state management has become one of PHP's built-in features.
You can use the state Management feature to manage all relevant variables in the period from the time the user enters the site until it leaves the site (as long as the user does not leave the site, these variables can be used, not because the user leaves a single page to cause the data to disappear), without the need to store many cookies Or even storing these variables in a database, using hidden form fields, causes a heavy load on the database server.
Once you activate state management on a page in the site, the PHP engine will start recording the user status (if the user is not already logged on to the audience), or continue to record a previously activated user status. To activate the state management feature of PHP, you can use the following syntax:
Session_Start ();
Once the state management is activated, PHP transmits a unique status code via a cookie (this code looks like the 940f8b05a40d5119c030c9c7745aead9) to the user, while on the server side, PHP The engine automatically generates a staging text file (for example: SESS_940F8B05A40D5119C030C9C7745AEAD9) with a file name corresponding to the status code, which is used to store all variables registered by the programmer in the user's state record.
When it comes to user state management, the most commonly used example is a page access counter (Access counter): Now I'm going to teach you how to write PHP program code.
Special attention
Before you try to activate the user status record, you must not be able to output anything (no spaces, tabs or even line breaks, no HTML labels, no content) to the browser. This is because the state management-related function sends the HTTP header (header) information to the browser, and the system will receive an error message if something else has been output before the HTTP header information is sent to the browser.
If the user's state management has not yet been activated, the following line of the program activates the user's state management:
Session_Start ();
Next, register a variable named count:
Session_register (' count ');
Once you have registered a variable, PHP will automatically maintain the value of the variable for you throughout the browsing process from the user's access to the site until it leaves the site, and you can take these registered variables at any time. The newly registered variable does not specify any value to it, but once we increase the value of the count variable, it will be 1:
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