What's better at freeing memory with PHP: unset() or $var = null

Question

I realise the second one avoids the overhead of a function call (update, is actually a language construct), but it would be interesting to know if one is be

Answer 1

unset is not actually a function, but a language construct. It is no more a function call than a return or an include.

Aside from performance issues, using unset makes your code's intent much clearer.