PHP Detailed explanation of built-in SERVER array

$_SERVER['PHP_SELF'] #The file name of the currently executing script, which is related to the document root.
$_SERVER['argv'] #The parameters passed to the script.
$_SERVER['argc'] # contains the number of command line parameters passed to the program (if running in command line mode).
$_SERVER['GATEWAY_INTERFACE'] #The version of the CGI specification used by the server. For example, "CGI/1.1".
$_SERVER['SERVER_NAME'] #The name of the server host where the script is currently running.
$_SERVER['SERVER_SOFTWARE'] #The string of server identification, which is given in the header when responding to the request.
$_SERVER['SERVER_PROTOCOL'] #The name and version of the communication protocol when requesting the page. For example, "HTTP/1.0".
$_SERVER['REQUEST_METHOD'] #Request method when visiting the page. For example: "GET", "HEAD", "POST", "PUT".
$_SERVER['QUERY_STRING'] #Query (query) string.
$_SERVER['DOCUMENT_ROOT'] #The document root directory where the currently running script is located. Defined in the server configuration file.
$_SERVER['HTTP_ACCEPT'] #The Accept: header content of the current request.
$_SERVER['HTTP_ACCEPT_CHARSET'] #Accept-Charset of the current request: The content of the header. For example: "iso-8859-1,*,utf-8".
$_SERVER['HTTP_ACCEPT_ENCODING'] #Accept-Encoding of the current request: the content of the header. For example: "gzip".
$_SERVER['HTTP_ACCEPT_LANGUAGE']# The content of the Accept-Language: header of the current request. For example: "en".
$_SERVER['HTTP_CONNECTION'] #The content of the Connection: header of the current request. For example: "Keep-Alive".
$_SERVER['HTTP_HOST'] #The content of the Host: header of the current request.
$_SERVER['HTTP_REFERER'] #Link to the URL address of the previous page of the current page.
$_SERVER['HTTP_USER_AGENT'] #User_Agent of the current request: header content.
$_SERVER['HTTPS'] — If accessed via https, it is set to a non-empty value (on), otherwise it returns off
$_SERVER['REMOTE_ADDR'] #The IP address of the user who is browsing the current page.
$_SERVER['REMOTE_HOST'] #The host name of the user who is browsing the current page.
$_SERVER['REMOTE_PORT'] #The port used by the user to connect to the server.
$_SERVER['SCRIPT_FILENAME'] #The absolute path name of the currently executing script.
$_SERVER['SERVER_ADMIN'

$_SERVER['SERVER_SIGNATURE'] #A string containing the server version and virtual host name.
$_SERVER['PATH_TRANSLATED'] #The base path of the file system (not the document root directory) where the current script is located.
$_SERVER['SCRIPT_NAME'] # contains the path of the current script. This is very useful when the page needs to point to itself.
$_SERVER['REQUEST_URI'] #URI required to access this page. For example, "/index.html".
$_SERVER['PHP_AUTH_USER'] #When PHP runs in Apache module mode and is using HTTP authentication, this variable is the username entered by the user.
$_SERVER['PHP_AUTH_PW'] #When PHP runs in Apache module mode and is using HTTP authentication, this variable is the password entered by the user.
$_SERVER['AUTH_TYPE'] #When PHP is running in Apache module mode, and HTTP authentication is being used, this variable is the type of authentication.