regression in HEAD since last week?

Just noticed that something changed in HEAD since last week. We have some code that does this: class foo { function foo() { $this['data'] = array(); } } last week that ran fine, this week it gives me an error: 'Cannot use object of type foo as an array'. I agree that the code above looks suspect, and that changing it to $this->data = array() works fine, I just wanted to point out the behaviour change since last week. --Wez.