When I migrated from PHP3 to PHP4 this script didn't work any more.
I don't have connection problems and the error appears just in some cases. 
The following is an ad-hoc script that reproduce the odbc error. 

// PHP Version 4.0.4pl1
// OS: Solaris 2.7
// Driver: ODBC-Openlink multi-tier 3.2
// this connection works fine.

  $conn_id = odbc_connect("Driver=/psitio/openlink/odbcsdk/lib/oplodbc.so.1;Host=sql02.local;SVT=SQLServer 7;UID=batalla_web;PWD=mundial86;DATABASE=elsitiodb2;FetchBufferSize=40000","","");

  echo "my connection $conn_id<BR>";

  $qry = "SELECT P.* FROM REAL_CAT_PADRE P WHERE IDIOMA = '" . $idioma . "' "
                        . "AND P.ID_PADRE IN (SELECT H.ID_HIJO FROM REAL_CAT_HIJO H WHERE "
                        . " H.ID_PADRE = '" . $cat . "') ";

  // this query works.
  $qry = "SELECT * FROM REAL_CAT_HIJO";

  // this query doesn't work IN PHP4 but works fine in PHP3 with the same ODBC-OPENLINK drive(??).
  $qry = "SELECT idvalor,Valor,Tipo_rango FROM Fot_atributo_valor WHERE idcanal=41 AND idaplic=1 AND idatrib=2 ORDER BY idvalor";

  $res_id = odbc_prepare($conn_id,$qry);

  // the error occur in this code line (IN PHP4).
  $result = odbc_execute($res_id);


Thanks in advance.

Nico.