TOR does not supply any server headers such as X_FORWARDED_FOR, so your best bet is to use a list of all known exit nodes. A list can be found at https://torstat.xenobite.eu/.
For other proxies, you can look at server headers. Possible server headers of interest include:
HTTP_VIA
HTTP_X_FORWARDED_FOR
HTTP_FORWARDED_FOR
HTTP_X_FORWARDED
HTTP_FORWARDED
HTTP_CLIENT_IP
HTTP_FORWARDED_FOR_IP
VIA
X_FORWARDED_FOR
FORWARDED_FOR
X_FORWARDED FORWARDED
CLIENT_IP
FORWARDED_FOR_IP
HTTP_PROXY_CONNECTION
In PHP, you can get the value of these fields in the $_SERVER[] superglobal
.