reason for "Warning: ociparse(): supplied argument is not a valid

hi all,
pls help me
i am getting error while retreving data from oracle

database...(through PHP)
connection is successful...
error is
"Warning: ociparse(): supplied argument is not a valid

OCI8-Connection resource on line "
what could be the reason of this error?
part of my script is below:
<?php
include("connect.inc.php");
$objoracon= new Connect();
$objoracon->start_connectoracle();
echo"successful connection";

$query4=OCIParse($objoracon,"select staff_enname from

hr_staff_mast");
?>
error is on line
$query4=OCIParse($objoracon,"select staff_enname from

hr_staff_mast");

pls help me to solve this pbm
thanx
ckb