Use Field definitions for objects
mainTo avoid using hardcoded strings and to benefit from validation, use the field definition classes located in the FacebookAds\Object\Fields namespace. You can use these constants with setData() or via direct property assignment.
// Using field definitions with setData
$someObject->setData(array(
MyObjectFields::ID => 1234,
MyObjectFields::NAME => 'My Name',
));
// Using field definitions with direct assignation
$someObject->{SomeObjectFields::ID} = 123;
// Equivalent to using string names
$someObject->id = 123;