$_SERVER['PHP_SELF']    Returns the filename of the currently executing script
$_SERVER['GATEWAY_INTERFACE']   Returns the version of the Common Gateway Interface (CGI) the server is using
$_SERVER['SERVER_ADDR']     Returns the IP address of the host server
$_SERVER['SERVER_NAME']     Returns the name of the host server (such as www.w3schools.com)
$_SERVER['SERVER_SOFTWARE']     Returns the server identification string (such as Apache/2.2.24)
$_SERVER['SERVER_PROTOCOL']     Returns the name and revision of the information protocol (such as HTTP/1.1)
$_SERVER['REQUEST_METHOD']  Returns the request method used to access the page (such as POST)
$_SERVER['REQUEST_TIME']    Returns the timestamp of the start of the request (such as 1377687496)
$_SERVER['QUERY_STRING']    Returns the query string if the page is accessed via a query string
$_SERVER['HTTP_ACCEPT']     Returns the Accept header from the current request
$_SERVER['HTTP_ACCEPT_CHARSET']     Returns the Accept_Charset header from the current request (such as utf-8,ISO-8859-1)
$_SERVER['HTTP_HOST']   Returns the Host header from the current request
$_SERVER['HTTP_REFERER']    Returns the complete URL of the current page (not reliable because not all user-agents support it)
$_SERVER['HTTPS']   Is the script queried through a secure HTTP protocol
$_SERVER['REMOTE_ADDR']     Returns the IP address from where the user is viewing the current page
$_SERVER['REMOTE_HOST']     Returns the Host name from where the user is viewing the current page
$_SERVER['REMOTE_PORT']     Returns the port being used on the user's machine to communicate with the web server
$_SERVER['SCRIPT_FILENAME']     Returns the absolute pathname of the currently executing script
$_SERVER['SERVER_ADMIN']    Returns the value given to the SERVER_ADMIN directive in the web server configuration file (if your script runs on a virtual host, it will be the value defined for that virtual host) (such as someone@w3schools.com)
$_SERVER['SERVER_PORT']     Returns the port on the server machine being used by the web server for communication (such as 80)
$_SERVER['SERVER_SIGNATURE']    Returns the server version and virtual host name which are added to server-generated pages
$_SERVER['PATH_TRANSLATED']     Returns the file system based path to the current script
$_SERVER['SCRIPT_NAME']     Returns the path of the current script
$_SERVER['SCRIPT_URI']  Returns the URI of the current page