Error: Data structure returned is not convertible in the requested format: Multidimensional column values not supported. Found unexpected array value for column 'unionOfSegments' in row '57': 'array ( 0 => 'customVariableName1', 1 => 'customVariableName2', 2 => 'customVariableName3', 3 => 'customVariableName4', 4 => 'customVariableName5', )'. Try to call this method with the parameters '&format=original&serialize=1'; you will get the original php data structure serialized.