PHP

$_SERVER['REMOTE_ADDR']

The $_SERVER['REMOTE_ADDR'] variable tells you the ip address of the visitor's machine that is being used to access your page. This has many uses like barring a certain ip address from accessing yor pages or serving up different content to different countries dynamically, etc.

Use as follows:

echo $_SERVER['REMOTE_ADDR'];

Using the $_SERVER['REMOTE_ADDR'] on this page will output the following (which is the ip from which you are accessing this page):

38.103.63.59

If your visitor is connecting to the internet through a proxy, then the above might show the ip of the proxy and not the true ip of the user's computer. In this case, you can use $_SERVER['HTTP_X_FORWARDED_FOR'] as follows:

echo $_SERVER['HTTP_X_FORWARDED_FOR'];

See also:

$_SERVER['HTTP_REFERER']

$_SERVER['HTTP_USER_AGENT']

$_SERVER['PHP_SELF']

$_SERVER['REQUEST_URI']

$_SERVER['DOCUMENT_ROOT']

$_SERVER['HTTP_HOST']

$_SERVER['QUERY_STRING']

$_SERVER['SCRIPT_FILENAME']