adding parameters to overridden method E_STRICT observation

Question

It appears (PHP 5.3) that if you are overriding a class method, it is okay to you can add additional parameters, as long as they have default values.

For

Answer 1

If you add a non-defaulted parameter to an overridden method, the subclass no longer satisfies the contract defined by the superclass. You cannot correctly call test2->stuff(), because this method now expects a parameter - but the superclass says you should be able to call it without one. Hence the E_STRICT warning.

If you add a defaulted parameter though, you can still call test3->stuff() (from your example) - as the superclass expects - and so the contract is not broken. In fact, by adding the optional parameter, you have simply extended it.