getting last number from db

[Anon]

I have each title in my db with a unique id.
I have 300 entrys or so.
I am using PHP for the site.
I would like it return the last unique id in the db 'ps' from the table 'submit' from the field 'fid'

Ive seen it float around before i do not see it around now...
Thanks in advance.
Nick

[Anon]

$d=mysql_connect("ps","user","pass);
$query="select max(fid) from submit";
$res=mysql_query($query,$d);
$r=mysql_fetch_row($res);
$max_fid=$r[0];

or so...