This IF-ELSE statement populates a PBArrayInfo structure. If the array in the first value of a PBCallInfo structure is not null, it sets the value of the pArrayItemCount variable to the length of the array:

if ( !(ci->pArgs->GetAt(0)->IsNull()) )
{
   array = ci->pArgs->GetAt(0)->GetArray();
   pArrayInfo = session->GetArrayInfo (array);
   pArrayItemCount = session->GetArrayLength(array);
}
else
{
   // NULL array
pArrayItemCount = 0;
}