为什么在布尔值上访问数组索引不会引起任何类型的错误?

When I try to access an array by key which is not exists in this array, php will raise "undefined index" notice error. When I try to do the same on strings, "Illegal string offset " warning is raised. This is an expected behavior and I know how to deal with it.When I try to access an array by key which is n