Add 1 Year to current date ?

I've been through the php.net docs, and this newsgroup - and all seems
to be configured properly, but this statement is still not working:

switch ($level) {
  case 1:
  $nextyear = mktime(0,0,0,date("Y")+1,date("m"),date("d"));
  $nextyear = strftime("%Y%m%d",$nextyear);
  break;

< snip case >

   $query = "INSERT INTO users VALUES (NULL, '$username',
password('$userpassword'), $level, '$fname', '$lname', '$tel',
'$email', '$addr', '$city', '$prov', '$country', '$pcode', 'comm',
'$today', '$nextyear')";

Any ideas ? It's a date field in the table - it displays:
YYYY-MM-DD --> 2005-09-22

Thanks!
Received on Tue Oct 18 02:26:52 2005