PHPToolKit update cutomer examples?

Hi,

Can anyone point me to a PHPToolKit Customer Update example?  I'm having trouble understanding how I map Fields from looking at the purchase_order_update example.

I will have internalId for the record and wish to update the custom field:

  [13] => nsComplexObject Object                                                            (                                                                [nsComplexObject_type] => DateCustomFieldRef                                                                [nsComplexObject_namespace] => urn:core_2010_1.platform.webservices.netsuite.com        [internalId] => custentity_customereffectivedate 

I dumped the above from get example here.

Thanks!