SOAP API - Object name is not valid 20110 when create custom object

[Anonymous]

Hello, i am trying to use SOAP now

when i try to create custom object

it keep returning "Object name is not valid (20110)"

what's wrong?

i am using the sample php on this page

http://developers.marketo.com/documentation/soap/getcustomobjects/

thanks

[Anonymous]

You are receiving this error because the object does not exist in your Marketo instance, but unfortuanely we're not able to create custom objects within a partners sandbox.