$_SERVER

$_SERVER is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server. There is no guarantee that every web server will provide any of these; servers may omit some, or provide others not listed here. That said, a large number of these variables are accounted for in the » CGI/1.1 specification, so you should be able to expect those.

You may or may not find any of the following elements in $_SERVER.------

'PHP_SELF'--

The filename of the currently executing script, relative to the document root. For instance, $_SERVER['PHP_SELF'] in a script at the address http://example.com/test.php/foo.bar would be /test.php/foo.bar. The __FILE__ constant contains the full path and filename of the current (i.e. included) file. If PHP is running as a command-line processor this variable contains the script name since PHP 4.3.0. Previously it was not available. 

 

'GATEWAY_INTERFACE'---

What revision of the CGI specification the server is using; i.e. 'CGI/1.1'. 

 

'SERVER_ADDR'

The IP address of the server under which the current script is executing.

 

'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; i.e. 'HTTP/1.0';

 

'REQUEST_TIME'

The timestamp of the start of the request. Available since PHP 5.1.0. It is float with microseconds since PHP 5.4.0. 

 

'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. 

 

'REMOTE_ADDR'

The IP address from which the user is viewing the current page. 

 

'REMOTE_HOST'

The Host name from which the user is viewing the current page. The reverse dns lookup is based off the REMOTE_ADDR of the user. 

 

'REMOTE_PORT'

The port being used on the user's machine to communicate with the web server. 

 

'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. For default setups, this will be '80'; using SSL, for instance, will change this to whatever your defined secure HTTP port is. 

 

'SERVER_SIGNATURE'

String containing the server version and virtual host name which are added to server-generated pages, if enabled.

Example--

 $_SERVER example

<?php      echo $_SERVER['SERVER_NAME'];?>