Description:
------------
hi

interface Y{}
class A implements Y{}
class B extends A{}

echo (is_subclass_of("A", "Y") ? "TRUE" : "FALSE")."\n";  // false: incorrect
echo (is_subclass_of("B", "Y") ? "TRUE" : "FALSE")."\n";  // true: correct


is_subclass_of must includes interfaces or not,
not sometimes not and sometimes yes

thank you