$object=db_use('query', "SELECT * FROM users WHERE `username`='$user' AND `user_password`='".md5($passwd)."';" );
if (mysql_num_rows($object)=='1')
{
include_once ('database.php');
$object=db_use('query', "SELECT * FROM users WHERE `username`='$user' AND `user_password`='".md5($passwd)."';" );
$row=mysql_fetch_array($object);
$user_id = $row[ "id" ];
session_register( "user_id" );
echo  "Вход закончен" ;
}

Warning: session_register() [function.session-register]: Cannot send session cookie - headers already sent by (output started at g:\work\domen.ru\www\enter.php: 5 ) in g:\work\domen.ru\www\enter.php on line  169 

Warning: session_register() [function.session-register]: Cannot send session cookie - headers already sent by (output started at g:\work\domen.ru\www\enter.php: 5 ) in g:\work\domen.ru\www\enter.php on line  169 
Вход закончен