Why doesn't this work? HTTP_USER_AGENT

I have this small test page, below, which returns an error - Parse error: parse error in /usr/local/apache/htdocs/test.php on line 4 on the $browser line, if I comment it out, it returns an error on the $ip line, etc. I can leave all the php lines out, add an echo statement <? echo $HTTP_USER_AGENT ?> in the body to get the http_user_agent and it displays the user agent just fine. What have I done wrong in such a simple bit of code? ------------------------- <html><head><title></title></head> <body> <? $browser = $HTTP_USER_AGENT; $ip = $REMOTE_ADDR ; $db = mysql_connect ( "localhost" , "username" , "password" ); mysql_select_db ( "database" , $db ); $sql  =  "INSERT INTO table_name(ip,browser,received)  VALUES('$ip','$browser',now())" ; $results  =  mysql_query ( $sql); ?> <h1>Howdy</h1> </body></html> -------------------------------- TIA, Chip