From global scope:
Bar::y($a = 2)
Bar::y($b = 3)
Bar::y($c = 99)
Foo::x($a = 1)
Foo::x($b = 3)
Foo::x($c = 99)

From class context:
Bar::y($a = 2)
Bar::y($b = 3)
Bar::y($c = 99)
Foo::x($a = 1)
Foo::x($b = 3)
Foo::x($c = 99)