Then: mb_substr ( string $str , int $start [, int $length [, string $encoding ]] ) If you implement mb_substr yourself, the efficiency is not very good. Usage of encoding-related php functions ord(substr($str, $i, 1)) > 0xa0) ord($string) returns the ASC code of the first character of the string. This can be used to determine whether the first character of the intercepted string is a Chinese character, because for example, a text encoded by gb2312 is 2 bytes, and utf8 is three characters. Festival. That is, any code greater than 256 is a Chinese character. Regular characters:
Encoding conversion
url encoding urlencode All non-alphanumeric characters except -_. in the returned string after encoding will be replaced with a percent sign (%) followed by two hexadecimal digits, and spaces are encoded as plus signs (+). This encoding is the same as the encoding of WWW form POST data, and the same encoding as the application/x-www-form-urlencoded media type. Note: Only part of the URL should be encoded when encoding, otherwise colons and backslashes in the URL will also be escaped. URLEncode generally has two methods, one is the traditional Encode based on GB2312, and the other is the Encode based on UTF-8. For example:
For example, we use the browser to open Baidu and search for "China". In the address bar we see: http://www.baidu.com/s?wd=%E4%B8%AD%E5%9B%BD&rsv_bp=0&ch=&tn=baidu&bar=&rsv_spt=3&ie=utf-8&rsv_sug3=16&rsv_sug=0&rsv_sug4=302&rsv_sug1=11&inputT=22928 That is, we see that "China" is automatically converted by the browser to: %E4%B8%AD%E5%9B%BD. The difference between urlencode and rawurlencode: urlencode encodes spaces as a plus sign "+", and rawurlencode encodes spaces as a plus sign "%20". url decoding urldecode and rawurldecode 1. When decoding, you can use the corresponding urldecode() and rawurldecode(). Correspondingly, rawurldecode() will not decode the plus sign ('+') into a space, but urldecode() can. 2. The decoded string by urldecode() and rawurldecode() is encoded in UTF-8 format. If the URL contains non-UTF-8 encoded Chinese, the decoded string must be converted. As follows, first set the php file to gb2312 encoding. You will see that part of it is garbled and part of it is normal.
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Effective methods to prevent session fixed attacks include: 1. Regenerate the session ID after the user logs in; 2. Use a secure session ID generation algorithm; 3. Implement the session timeout mechanism; 4. Encrypt session data using HTTPS. These measures can ensure that the application is indestructible when facing session fixed attacks.

Implementing session-free authentication can be achieved by using JSONWebTokens (JWT), a token-based authentication system where all necessary information is stored in the token without server-side session storage. 1) Use JWT to generate and verify tokens, 2) Ensure that HTTPS is used to prevent tokens from being intercepted, 3) Securely store tokens on the client side, 4) Verify tokens on the server side to prevent tampering, 5) Implement token revocation mechanisms, such as using short-term access tokens and long-term refresh tokens.

The security risks of PHP sessions mainly include session hijacking, session fixation, session prediction and session poisoning. 1. Session hijacking can be prevented by using HTTPS and protecting cookies. 2. Session fixation can be avoided by regenerating the session ID before the user logs in. 3. Session prediction needs to ensure the randomness and unpredictability of session IDs. 4. Session poisoning can be prevented by verifying and filtering session data.

To destroy a PHP session, you need to start the session first, then clear the data and destroy the session file. 1. Use session_start() to start the session. 2. Use session_unset() to clear the session data. 3. Finally, use session_destroy() to destroy the session file to ensure data security and resource release.

How to change the default session saving path of PHP? It can be achieved through the following steps: use session_save_path('/var/www/sessions');session_start(); in PHP scripts to set the session saving path. Set session.save_path="/var/www/sessions" in the php.ini file to change the session saving path globally. Use Memcached or Redis to store session data, such as ini_set('session.save_handler','memcached'); ini_set(

TomodifydatainaPHPsession,startthesessionwithsession_start(),thenuse$_SESSIONtoset,modify,orremovevariables.1)Startthesession.2)Setormodifysessionvariablesusing$_SESSION.3)Removevariableswithunset().4)Clearallvariableswithsession_unset().5)Destroythe

Arrays can be stored in PHP sessions. 1. Start the session and use session_start(). 2. Create an array and store it in $_SESSION. 3. Retrieve the array through $_SESSION. 4. Optimize session data to improve performance.

PHP session garbage collection is triggered through a probability mechanism to clean up expired session data. 1) Set the trigger probability and session life cycle in the configuration file; 2) You can use cron tasks to optimize high-load applications; 3) You need to balance the garbage collection frequency and performance to avoid data loss.


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