$_SERVER is a superglobal variable which holds the data about the headers, script locations, network addresses, paths, etc.
Example:
<?php
echo $_SERVER['PHP_SELF'] . '<br>';
echo $_SERVER['DOCUMENT_ROOT'] . '<br>';
echo $_SERVER['SERVER_ADDR'] . '<br>';
echo $_SERVER['SERVER_NAME'] . '<br>';
echo $_SERVER['REQUEST_METHOD'] . '<br>';
echo $_SERVER['REQUEST_TIME'] . '<br>';
echo $_SERVER['HTTP_USER_AGENT'] . '<br>';
echo $_SERVER['REMOTE_ADDR'];
?>
The following table lists some of the important elements of $_SERVER:
| Element/Code | Description |
|---|---|
| $_SERVER['PHP_SELF'] | Returns the filename of the currently executing script |
| $_SERVER['GATEWAY_INTERFACE'] | Returns the version of the Common Gateway Interface 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 |
| $_SERVER['SERVER_SOFTWARE'] | Returns the server identification string |
| $_SERVER['SERVER_PROTOCOL'] | Returns the name and revision of the information protocol |
| $_SERVER['REQUEST_METHOD'] | Returns the request method used to access the page |
| $_SERVER['REQUEST_TIME'] | Returns the timestamp of the start of the request |
| $_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 |
| $_SERVER['HTTP_HOST'] | Returns the Host header from the current request |
| $_SERVER['HTTP_REFERER'] | Returns the complete URL of the current page |
| $_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 Hostname 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 |
| $_SERVER['SERVER_PORT'] | Returns the port on the server machine being used by the web server for communication |
| $_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 |
