Limit postgresql query results

Hello, I am using PostgreSQL 6.3 and PHP. I am trying to build a query that
only returns 20 results at a time, with a "next" link at the bottom of the
query results for the next 20. Someone suggested to me that I use the below
block of code (pg_Exec ($conn, "set QUERY_LIMIT='20'");). How would I use
this in the below code I'm already using to connect to and query the DB? And
does anyone maybe have any better ideas of going about this task?

CODE I WAS GIVEN TO USE
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pg_Exec ($conn, "set QUERY_LIMIT='20'");
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THE CODE I AM USING NOW
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<SCRIPT language="PHP">

$conn = pg_Connect("Localhost", "5432", "", "", "contacts");
if (!$conn) {

echo "An error occurred.\n";
exit;
}

$result = pg_Exec($conn, "SELECT* FROM contacts_list");

if (!$result) {

echo "An error occurred.\n";
exit;
}

$num = pg_NumRows($result);
$i = 0;

while ($i < $num) {

echo "<TR><TD><font>";
echo pg_Result($result, $i, "personal_id");
echo "</font></TD><TD><font>";
echo pg_Result($result, $i, "name");
echo "</font></TD><TD><font>";
echo pg_Result($result, $i, "address");
echo "</font></TD><TD><font>";
echo pg_Result($result, $i, "city");
echo "</font></TD><TD><font>";
echo pg_Result($result, $i, "state");
echo "</font></TD><TD><font>";
echo pg_Result($result, $i, "zip_code");
echo "</font></center></TD><TD><center><font>";
echo pg_Result($result, $i, "phone_number");
echo "</font></center></TD></TR>";
$i++;
           }

pg_FreeResult($result);
pg_Close($conn);
</script>
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Thank you everyone for your help