Vendor Bill Posting Period PHP

I need to get a list of posting periods for a vendor bill and then set the posting period of the vendor bill to be one of the posting periods in PHP.  I figured out how to do it in C# but I have no experience with PHP and wondered if some PHP expert could help me.

The following is that code snippet that I need translated.  Any help would be appreciated.  Thanks.

                 GetSelectValueType type = new GetSelectValueType();                  type = GetSelectValueType.vendorBill_postingPeriod;                    GetSelectValueField field = new GetSelectValueField();                  field.fieldType = type;                  field.fieldTypeSpecified = true;                    getSelectValueResult response = service.getSelectValue(field);                    RecordRef postingPeriod = null;                    foreach (RecordRef recordRef in response.recordRefList)                  {                      //string postingPeriodString = recordRef.name;                      //string internalId = recordRef.internalId;                        if (recordRef.name == "May 2009")                      {                          postingPeriod = recordRef;                          break;                      }                  }                    VendorBill vendorBill = new VendorBill();                  vendorBill.postingPeriod = postingPeriod;