Summary of Obtaining Url and Physical Path in PHP_PHP Tutorial
Here I would like to summarize some information about getting the URL in the address bar and the path to which the file belongs:
Using $_SERVER[ ] we can accomplish many things: it is a header containing ( headers), an array of path information and script location. The entities of the array are created by the web server.
This is a "superglobal", or can be described as an automatic global variable. This just means that it works in all scripts. You do not need to use global $_SERVER; to access it within a function or method, as you would with $HTTP_SERVER_VARS. $HTTP_SERVER_VARS contains the same information, but is not an automatic global variable. (Note: $HTTP_SERVER_VARS and $_SERVER are different variables, and PHP handles them differently.) These variables are also available in all scripts if the register_globals directive is set; that is, the $_SERVER and $HTTP_SERVER_VARS arrays are separated.
$_SERVER['HTTP_HOST'] Gets the Host: header content of the current request
$_SERVER['PHP_SELF'] This may be the one we use most often. It returns the current calling page. File name, if it is http://localhost/test/2005/test.php, then it will return /test/2005/test.php
$_SERVER['SCRIPT_NAME'] which will return the current script. path. This is very useful when the page needs to point to itself
$_SERVER['SCRIPT_FILENAME'] It will return the absolute path information where the current file is located
$_SERVER['REQUEST_URI'] Returns the location where this page is accessed The required URI, including "/"
Of course there are many path functions:
dirname(), which returns the directory part of the path information, preceded by "/"
basename() returns the basic file name part of the path. Of course, you can also set the suffix to control the output.
realpath(), returns the absolutely normalized path of the path information

The main advantages of using database storage sessions include persistence, scalability, and security. 1. Persistence: Even if the server restarts, the session data can remain unchanged. 2. Scalability: Applicable to distributed systems, ensuring that session data is synchronized between multiple servers. 3. Security: The database provides encrypted storage to protect sensitive information.

Implementing custom session processing in PHP can be done by implementing the SessionHandlerInterface interface. The specific steps include: 1) Creating a class that implements SessionHandlerInterface, such as CustomSessionHandler; 2) Rewriting methods in the interface (such as open, close, read, write, destroy, gc) to define the life cycle and storage method of session data; 3) Register a custom session processor in a PHP script and start the session. This allows data to be stored in media such as MySQL and Redis to improve performance, security and scalability.

SessionID is a mechanism used in web applications to track user session status. 1. It is a randomly generated string used to maintain user's identity information during multiple interactions between the user and the server. 2. The server generates and sends it to the client through cookies or URL parameters to help identify and associate these requests in multiple requests of the user. 3. Generation usually uses random algorithms to ensure uniqueness and unpredictability. 4. In actual development, in-memory databases such as Redis can be used to store session data to improve performance and security.

Managing sessions in stateless environments such as APIs can be achieved by using JWT or cookies. 1. JWT is suitable for statelessness and scalability, but it is large in size when it comes to big data. 2.Cookies are more traditional and easy to implement, but they need to be configured with caution to ensure security.

To protect the application from session-related XSS attacks, the following measures are required: 1. Set the HttpOnly and Secure flags to protect the session cookies. 2. Export codes for all user inputs. 3. Implement content security policy (CSP) to limit script sources. Through these policies, session-related XSS attacks can be effectively protected and user data can be ensured.

Methods to optimize PHP session performance include: 1. Delay session start, 2. Use database to store sessions, 3. Compress session data, 4. Manage session life cycle, and 5. Implement session sharing. These strategies can significantly improve the efficiency of applications in high concurrency environments.

Thesession.gc_maxlifetimesettinginPHPdeterminesthelifespanofsessiondata,setinseconds.1)It'sconfiguredinphp.iniorviaini_set().2)Abalanceisneededtoavoidperformanceissuesandunexpectedlogouts.3)PHP'sgarbagecollectionisprobabilistic,influencedbygc_probabi

In PHP, you can use the session_name() function to configure the session name. The specific steps are as follows: 1. Use the session_name() function to set the session name, such as session_name("my_session"). 2. After setting the session name, call session_start() to start the session. Configuring session names can avoid session data conflicts between multiple applications and enhance security, but pay attention to the uniqueness, security, length and setting timing of session names.


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