Ecco qua il codice del download....

codice:
$info_all = "SELECT NOME_DOCUMENTO,TYPE_ALLEGATO FROM ***** WHERE IDALLEGATO = '$idAllegato'";
$stmt_info_all = oci_parse($dbh,$info_all);
$err_info_all  = @oci_execute($stmt_info_all);
controlErr($err_info_all,$stmt_info_all);
$row = oci_fetch_assoc($stmt_info_all);
$type_file = $row['TYPE_ALLEGATO'];
$name_file = $row['NOME_DOCUMENTO'];

//QUERY PER PRENDERE IL BLOB
$query = "SELECT ALLEGATO FROM ******* WHERE IDALLEGATO = :MYBLOBID";
$stmt_all = oci_parse ($dbh, $query);
oci_bind_by_name($stmt_all, ':MYBLOBID', $idAllegato);
oci_execute($stmt_all, OCI_DEFAULT);
$arr = oci_fetch_assoc($stmt_all);
$result = $arr['ALLEGATO']->load();
header("Content-type: $type_file");
header("Content-Disposition: attachment; filename=$name_file");
echo $result;
oci_free_statement($stmt);
oci_close($dbh);