$_SERVER['PHP_SELF'] #当前正在执行脚本的文件名,与 document root相关。 $_SERVER['argv'] #传递给该脚本的参数。 $_SERVER['argc'] #包含传递给程序的命令行参数的个数(如果运行在命令行模式)。 $_SERVER['GATEWAY_INTERFACE'] #服务器使用的 CGI 规范的版本。例如,“CGI/1.1”。 $_SERVER['SERVER_NAME'] #当前运行脚本所在服务器主机的名称。 $_SERVER['SERVER_SOFTWARE'] #服务器标识的字串,在响应请求时的头部中给出。 $_SERVER['SERVER_PROTOCOL'] #请求页面时通信协议的名称和版本。例如,“HTTP/1.0”。 $_SERVER['REQUEST_METHOD'] #访问页面时的请求方法。例如:“GET”、“HEAD”,“POST”,“PUT”。 $_SERVER['QUERY_STRING'] #查询(query)的字符串。 $_SERVER['DOCUMENT_ROOT'] #当前运行脚本所在的文档根目录。在服务器配置文件中定义。 $_SERVER['HTTP_ACCEPT'] #当前请求的 Accept: 头部的内容。 $_SERVER['HTTP_ACCEPT_CHARSET'] #当前请求的 Accept-Charset: 头部的内容。例如:“iso-8859-1,*,utf-8”。 $_SERVER['HTTP_ACCEPT_ENCODING'] #当前请求的 Accept-Encoding: 头部的内容。例如:“gzip”。 $_SERVER['HTTP_ACCEPT_LANGUAGE']#当前请求的 Accept-Language: 头部的内容。例如:“en”。 $_SERVER['HTTP_CONNECTION'] #当前请求的 Connection: 头部的内容。例如:“Keep-Alive”。 $_SERVER['HTTP_HOST'] #当前请求的 Host: 头部的内容。 $_SERVER['HTTP_REFERER'] #链接到当前页面的前一页面的 URL 地址。 $_SERVER['HTTP_USER_AGENT'] #当前请求的 User_Agent: 头部的内容。 $_SERVER['REMOTE_ADDR'] #正在浏览当前页面用户的 IP 地址。 $_SERVER['REMOTE_HOST'] #正在浏览当前页面用户的主机名。 $_SERVER['REMOTE_PORT'] #用户连接到服务器时所使用的端口。 $_SERVER['SCRIPT_FILENAME'] #当前执行脚本的绝对路径名。 $_SERVER['SERVER_ADMIN'] #管理员信息 $_SERVER['SERVER_PORT'] #服务器所使用的端口 $_SERVER['SERVER_SIGNATURE'] #包含服务器版本和虚拟主机名的字符串。 $_SERVER['PATH_TRANSLATED'] #当前脚本所在文件系统(不是文档根目录)的基本路径。 $_SERVER['SCRIPT_NAME'] #包含当前脚本的路径。这在页面需要指向自己时非常有用。 $_SERVER['REQUEST_URI'] #访问此页面所需的 URI。例如,“/index.html”。 $_SERVER['PHP_AUTH_USER'] #当 PHP 运行在 Apache 模块方式下,并且正在使用 HTTP 认证功能,这个变量便是用户输入的用户名。 $_SERVER['PHP_AUTH_PW'] #当 PHP 运行在 Apache 模块方式下,并且正在使用 HTTP 认证功能,这个变量便是用户输入的密码。 $_SERVER['AUTH_TYPE'] #当 PHP 运行在 Apache 模块方式下,并且正在使用 HTTP 认证功能,这个变量便是认证的类型。
The above introduces the detailed introduction of $_SERVER in PHP, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.

In PHP, you can use session_status() or session_id() to check whether the session has started. 1) Use the session_status() function. If PHP_SESSION_ACTIVE is returned, the session has been started. 2) Use the session_id() function, if a non-empty string is returned, the session has been started. Both methods can effectively check the session state, and choosing which method to use depends on the PHP version and personal preferences.

Sessionsarevitalinwebapplications,especiallyfore-commerceplatforms.Theymaintainuserdataacrossrequests,crucialforshoppingcarts,authentication,andpersonalization.InFlask,sessionscanbeimplementedusingsimplecodetomanageuserloginsanddatapersistence.

Managing concurrent session access in PHP can be done by the following methods: 1. Use the database to store session data, 2. Use Redis or Memcached, 3. Implement a session locking strategy. These methods help ensure data consistency and improve concurrency performance.

PHPsessionshaveseverallimitations:1)Storageconstraintscanleadtoperformanceissues;2)Securityvulnerabilitieslikesessionfixationattacksexist;3)Scalabilityischallengingduetoserver-specificstorage;4)Sessionexpirationmanagementcanbeproblematic;5)Datapersis

Load balancing affects session management, but can be resolved with session replication, session stickiness, and centralized session storage. 1. Session Replication Copy session data between servers. 2. Session stickiness directs user requests to the same server. 3. Centralized session storage uses independent servers such as Redis to store session data to ensure data sharing.

Sessionlockingisatechniqueusedtoensureauser'ssessionremainsexclusivetooneuseratatime.Itiscrucialforpreventingdatacorruptionandsecuritybreachesinmulti-userapplications.Sessionlockingisimplementedusingserver-sidelockingmechanisms,suchasReentrantLockinJ

Alternatives to PHP sessions include Cookies, Token-based Authentication, Database-based Sessions, and Redis/Memcached. 1.Cookies manage sessions by storing data on the client, which is simple but low in security. 2.Token-based Authentication uses tokens to verify users, which is highly secure but requires additional logic. 3.Database-basedSessions stores data in the database, which has good scalability but may affect performance. 4. Redis/Memcached uses distributed cache to improve performance and scalability, but requires additional matching

Sessionhijacking refers to an attacker impersonating a user by obtaining the user's sessionID. Prevention methods include: 1) encrypting communication using HTTPS; 2) verifying the source of the sessionID; 3) using a secure sessionID generation algorithm; 4) regularly updating the sessionID.


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