PHP predefines $_SERVER instance, and all $_SERVER starting with are predefined service variables.

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<?<span>php
</span><span>header</span>("Content-type:text/html;charset=utf8"<span>);
</span><span>echo</span> "error_reporting=>".<span>error_reporting</span>(<span>E_ALL</span>)."<br>"<span>;

</span><span>echo</span> "PHP_SELF=>".<span>$_SERVER</span>['PHP_SELF']."<br>"; <span>#</span><span>当前正在执行脚本的文件名，与 document root相关。</span><span>echo</span> "argv=>".<span>$_SERVER</span>['argv']."<br>"; <span>#</span><span>传递给该脚本的参数。</span><span>echo</span> "argc=>".<span>$_SERVER</span>['argc']."<br>"; <span>#</span><span>包含传递给程序的命令行参数的个数（如果运行在命令行模式）。</span><span>echo</span> "GATEWAY_INTERFACE=>".<span>$_SERVER</span>['GATEWAY_INTERFACE']."<br>"; <span>#</span><span>服务器使用的 CGI 规范的版本。例如，“CGI/1.1”。</span><span>echo</span> "SERVER_NAME=>".<span>$_SERVER</span>['SERVER_NAME']."<br>"; <span>#</span><span>当前运行脚本所在服务器主机的名称。</span><span>echo</span> "SERVER_SOFTWARE=>".<span>$_SERVER</span>['SERVER_SOFTWARE']."<br>"; <span>#</span><span>服务器标识的字串，在响应请求时的头部中给出。</span><span>echo</span> "SERVER_PROTOCOL=>".<span>$_SERVER</span>['SERVER_PROTOCOL']."<br>"; <span>#</span><span>请求页面时通信协议的名称和版本。例如，“HTTP/1.0”。</span><span>echo</span> "REQUEST_METHOD=>".<span>$_SERVER</span>['REQUEST_METHOD']."<br>"; <span>#</span><span>访问页面时的请求方法。例如：“GET”、“HEAD”，“POST”，“PUT”。</span><span>echo</span> "REQUEST_TIME=>".<span>date</span>("Y-m-d H:s:i", <span>$_SERVER</span>['REQUEST_TIME'])."<br>"; <span>#</span><span>请求开始的时间戳</span><span>echo</span> "QUERY_STRING=>".<span>$_SERVER</span>['QUERY_STRING']."<br>"; <span>#</span><span>查询(query)的字符串。</span><span>echo</span> "DOCUMENT_ROOT=>".<span>$_SERVER</span>['DOCUMENT_ROOT']."<br>"; <span>#</span><span>当前运行脚本所在的文档根目录。在服务器配置文件中定义。</span><span>echo</span> "HTTP_ACCEPT=>".<span>$_SERVER</span>['HTTP_ACCEPT']."<br>"; <span>#</span><span>当前请求的 Accept: 头部的内容。</span><span>echo</span> "HTTP_ACCEPT_CHARSET=>".<span>$_SERVER</span>['HTTP_ACCEPT_CHARSET']."<br>"; <span>#</span><span>当前请求的 Accept-Charset: 头部的内容。例如：“iso-8859-1,*,utf-8”。</span><span>echo</span> "HTTP_ACCEPT_ENCODING=>".<span>$_SERVER</span>['HTTP_ACCEPT_ENCODING']."<br>"; <span>#</span><span>当前请求的 Accept-Encoding: 头部的内容。例如：“gzip”。</span><span>echo</span> "HTTP_ACCEPT_LANGUAGE=>".<span>$_SERVER</span>['HTTP_ACCEPT_LANGUAGE']."<br>"; <span>#</span><span>当前请求的 Accept-Language: 头部的内容。例如：“en”。</span><span>echo</span> "HTTP_C>$_SERVER['HTTP_CONNECTION']."<br>"; <span>#</span><span>当前请求的 Connection: 头部的内容。例如：“Keep-Alive”。</span><span>echo</span> "HTTP_HOST=>".<span>$_SERVER</span>['HTTP_HOST']."<br>"; <span>#</span><span>当前请求的 Host: 头部的内容。</span><span>echo</span> "HTTP_REFERER=>".<span>$_SERVER</span>['HTTP_REFERER']."<br>"; <span>#</span><span>a标签跳转链接到当前页面的前一页面的 URL 地址。</span><span>echo</span> "HTTP_USER_AGENT=>".<span>$_SERVER</span>['HTTP_USER_AGENT']."<br>"; <span>#</span><span>当前请求的 User-Agent: 头部的内容。</span><span>echo</span> "HTTPS=>".<span>$_SERVER</span>['HTTPS']."<br>"; <span>#</span><span>如果通过https访问,则被设为一个非空的值(on)，否则返回off</span><span>echo</span> "REMOTE_ADDR=>".<span>$_SERVER</span>['REMOTE_ADDR']."<br>"; <span>#</span><span>正在浏览当前页面用户的 IP 地址。</span><span>echo</span> "REMOTE_HOST=>".<span>$_SERVER</span>['REMOTE_HOST']."<br>"; <span>#</span><span>正在浏览当前页面用户的主机名。</span><span>echo</span> "REMOTE_PORT=>".<span>$_SERVER</span>['REMOTE_PORT']."<br>"; <span>#</span><span>用户连接到服务器时所使用的端口。</span><span>echo</span> "SCRIPT_FILENAME=>".<span>$_SERVER</span>['SCRIPT_FILENAME']."<br>"; <span>#</span><span>当前执行脚本的绝对路径名。</span><span>echo</span> "SERVER_ADMIN=>".<span>$_SERVER</span>['SERVER_ADMIN']."<br>"; <span>#</span><span>管理员信息</span><span>echo</span> "SERVER_PORT=>".<span>$_SERVER</span>['SERVER_PORT']."<br>"; <span>#</span><span>服务器所使用的端口</span><span>echo</span> "SERVER_SIGNATURE=>".<span>$_SERVER</span>['SERVER_SIGNATURE']."<br>"; <span>#</span><span>包含服务器版本和虚拟主机名的字符串。</span><span>echo</span> "PATH_TRANSLATED=>".<span>$_SERVER</span>['PATH_TRANSLATED']."<br>"; <span>#</span><span>当前脚本所在文件系统（不是文档根目录）的基本路径。</span><span>echo</span> "SCRIPT_NAME=>".<span>$_SERVER</span>['SCRIPT_NAME']."<br>"; <span>#</span><span>包含当前脚本的路径。这在页面需要指向自己时非常有用。</span><span>echo</span> "REQUEST_RUI=>".<span>$_SERVER</span>['REQUEST_URI']."<br>"; <span>#</span><span>访问此页面所需的 URI。例如，“/index.html”。</span><span>echo</span> "__FILE__=>".<span>__FILE__</span>."<br>";

The above introduces the PHP predefined $_SERVER instance. All $_SERVER starting with are predefined service variables. , including relevant content, I hope it will be helpful to friends who are interested in PHP tutorials.