Here is a list of Apache Server Variables you can try:

• HTTP_HOST
• HTTP_USER_AGENT
• HTTP_ACCEPT
• HTTP_ACCEPT_LANGUAGE
• HTTP_ACCEPT_ENCODING
• HTTP_ACCEPT_CHARSET
• HTTP_KEEP_ALIVE
• HTTP_CONNECTION
• SERVER_SIGNATURE
• SERVER_SOFTWARE
• SERVER_NAME
• SERVER_ADDR
• SERVER_PORT
• REMOTE_ADDR
• DOCUMENT_ROOT
• SERVER_ADMIN
• SCRIPT_FILENAME
• REMOTE_PORT
• GATEWAY_INTERFACE
• SERVER_PROTOCOL
• REQUEST_METHOD
• QUERY_STRING
• REQUEST_URI
• SCRIPT_NAME