| SERVER_NAME | The host name (or the IP address) where the script is running. |
| SERVER_SOFTWARE | The server software used. Examples: CERN/3.0 or NCSA/1.3 |
| GATEWAY_INTERFACE | CGI version running on the server |
| SERVER_PROTOCOL | Used HTTP protocol version. It should be CGI/1.1 |
| SERVER_PORT | TCP port to which the server is connected to. Usually its value is 80 |
| REQUEST_METHOD | The used method: GET or POST |
| HTTP_ACCEPT | A Content-type list the browser can handle |
| HTTP_USER_AGENT | The browser's name that sent information. This variable usually contains the browser's name, its version number and other information such as the platform where it is running |
| HTTP_REFERER | The URL of the document which contains the form |
| PATH_INFO | The URL and additional information sent by the browser when the GET method is used (see Dissecting the simplest CGI script: Hello Net! for more information) |
| PATH_TRANSLATED | The real system's path contained inside of PATH_INFO variable |
| SCRIPT_NAME | The script's name and the path |
| QUERY_STRING | Information sent by means of the GET method. In other words all information sent after the '?' symbol inside of the URL |
| REMOTE_HOST | The host name which sent the request |
| REMOTE_ADDR | The host address which sent the request |
| REMOTE_USER | The user name of who sent the request (when an authentication is available) |
| REMOTE_IDENT | The server name which sent the request (when the ident protocol is available) |
| CONTENT_TYPE | When the POST method is used, its value is: 'application/x-www-form-urlencoded'. When a file is sent, its value is: 'multipart/form-data' |
| CONTENT_LENGTH | When the POST method is used, its value define the input standard size. In other words the number of bytes sent |