PHP_SELF=The filename of the currently executing script, relative to the document root.
argv=Array of arguments passed to the script. When the script is run on the command line, this gives C-style access to the command line parameters. When called via the GET method, this will contain the query string.
argc=Contains the number of command line parameters passed to the script (if run on the command line).
GATEWAY_INTERFACE=What revision of the CGI specification the server is using.
SERVER_NAME=The name of the server host under which the current script is executing. If the script is running on a virtual host, this will be the value defined for that virtual host.
SERVER_SOFTWARE=Server identification string, given in the headers when responding to requests.
SERVER_PROTOCOL=Name and revision of the information protocol via which the page was requested. Example: 'HTTP/1.0'.
REQUEST_METHOD=Which request method was used to access the page. Example: 'GET', 'HEAD', 'POST', 'PUT'.
QUERY_STRING=The query string, if any, via which the page was accessed.
DOCUMENT_ROOT=The document root directory under which the current script is executing, as defined in the server's configuration file.
HTTP_ACCEPT=Contents of the Accept: header from the current request, if there is one.
HTTP_ACCEPT_CHARSET=Contents of the Accept-Charset: header from the current request, if there is one.
HTTP_ACCEPT_ENCODING=Contents of the Accept-Encoding: header from the current request, if there is one.
HTTP_ACCEPT_LANGUAGE=Contents of the Accept-Language: header from the current request, if there is one.
HTTP_CONNECTION=Contents of the Connection: header from the current request, if there is one. Example: 'Keep-Alive'.
HTTP_HOST=Contents of the Host: header from the current request, if there is one.
HTTP_REFERER=The address of the page (if any) which referred the user agent to the current page. This is set by the user agent. Not all user agents will set this, and some provide the ability to modify HTTP_REFERER as a feature. In short, it cannot really be trusted.
HTTP_USER_AGENT=Contents of the User_Agent: header from the current request, if there is one. This is a string denoting the user agent being which is accessing the page.
REMOTE_ADDR=The IP address from which the user is viewing the current page.
REMOTE_PORT=The port being used on the user's machine to communicate with the web server.
SCRIPT_FILENAME=The absolute pathname of the currently executing script.
SERVER_ADMIN=The value given to the SERVER_ADMIN (for Apache) directive in the web server configuration file. If the script is running on a virtual host, this will be the value defined for that virtual host.
SERVER_PORT=The port on the server machine being used by the web server for communication.
SERVER_SIGNATURE=String containing the server version and virtual host name which are added to server-generated pages, if enabled.
PATH_TRANSLATED=Filesystem- (not document root-) based path to the current script, after the server has done any virtual-to-real mapping.
SCRIPT_NAME=Contains the current script's path. This is useful for pages which need to point to themselves.
REQUEST_URI=The URI which was given in order to access this page.
