Converting PHP function mysql_data_seek to PostgreSQL

Hi!

I have this little snipnet of PHP code that calls the mysql_data_seek
function, and I need to convert
it to something similar to work with PostgreSQL. This is used basically to
jump to a specific row
position for an open query. Do I need to define and use a cursor to do this
with Postgres?

function data_seek($pos,$query_id=-1) {
// goes to row $pos
if ($query_id!=-1) {
$this->query_id=$query_id;
}
return mysql_data_seek($this->query_id, $pos);
}

Thanks in advance, any pointers would be helpful.

Chris Schreiber