PHP

$_SERVER['HTTP_HOST']

The $_SERVER['HTTP_HOST'] variable tells you the host name as per the http header.

Use as follows:

For http://somesite.com,

echo $_SERVER['HTTP_HOST'];

will return somesite.com

For http://www.somesite.com,

echo $_SERVER['HTTP_HOST'];

will return www.somesite.com

See also:

$_SERVER['HTTP_REFERER']

$_SERVER['HTTP_USER_AGENT']

$_SERVER['REMOTE_ADDR']

$_SERVER['PHP_SELF']

$_SERVER['REQUEST_URI']

$_SERVER['DOCUMENT_ROOT']

$_SERVER['QUERY_STRING']

$_SERVER['SCRIPT_FILENAME']