What's better at freeing memory with PHP: unset() or $var = null
<p>I realise the second one avoids the overhead of a function call (<strong>update</strong>, is actually a language construct), but it would be interesting to know if one is better than the other. I have been using <code>unset()</code> for most of my coding, but I've recently looked through a few respectable classes found off the net that use <code>$var = null</code> instead.</p>

<p>Is there a preferred one, and what is the reasoning?</p>
