Finally, I have successfully connect using "IBM Client Access OLE DB provider" with connection string format taken from http://www.connectionstrings.com/as-400#p60.
Provider=IBMDA400;Data Source=MY_SYSTEM_NAME;User Id=myUsername;Password=myPassword;Default Collection=MY_LIBRARY;
So my actual connection string using the parameters above is:
Provider=IBMDA400;Data Source=10.33.15.3;User Id=ICTDEV;Password=******;Default Collection=mm370lib;
I've been using this connection also in my PHP program using COM.
Here is the code snippet:
include('application/libraries/adodb5/adodb.inc.php');
$this->db = ADONewConnection('ado');
$dsn = "Provider=IBMDA400;Data Source=10.33.15.3;UserId=ICTDEV;Password=******;Default Collection=mm370lib;";
$this->db->PConnect($dsn);