This is how I add friends through php.
PHP Code:
$db->query_write("
REPLACE INTO " . TABLE_PREFIX . "userlist
(userid, relationid, type, friend)
VALUES
($userid2, $userid, 'buddy', 'yes'),
($userid, $userid2, 'buddy', 'yes')
");
$db->query_write("
UPDATE " . TABLE_PREFIX . "user
SET friendcount = friendcount + 1
WHERE userid IN ($userid2, " . $userid . ")
");
$db->query_write("
UPDATE " . TABLE_PREFIX . "user
SET friendreqcount = IF(friendreqcount > 0, friendreqcount - 1, 0)
WHERE userid = " . $userid
);
require_once(DIR . '/includes/functions_databuild.php');
build_userlist($userid);
build_userlist($userid2);