SELECT chunks

Hi,
Presently I am rewriting some legacy PHP code that uses queries
extensively.
Currently the SELECT statements return all required data on the first call,
and with that data stored in a $_SESSION array, displays the data in chunks
of 25 rows at a time, as requested. This works ok for data sets that are
relatively small, however sometimes the SQL may return over 1000 rows and
that is seriously slow.
The original develloper of the site fixed this by limiting returned records
to the top 200, which is somewhat inadequate.
What I beleive is the best approach is to query the data in chunks of 25 at
a time, but I don't know enough SQL to do this.
I would very much appreciate some help to implement the above method, or
perhaps someone has an even better idea?
The SQL is FoxPro and the engine ODBC.
TIA
Vince Morgan