title: the difference between unset and = null
body: <p>From a <a href="http://us2.php.net/manual/en/function.unset.php#86347" rel="noreferrer">random php.net post</a>:    </p>
  
  <blockquote>
    <p>If you are doing $whatever = null; then you are rewriting variable's
    data. You might get memory freed / shrunk faster, but it may steal CPU
    cycles from the code that truly needs them sooner, resulting in a
    longer overall execution time.</p>
  </blockquote>
  
  <p>Apparently this is the <a href="https://stackoverflow.com/a/13636996/1469439">undisputed truth</a> so maybe someone would be so kind as to explain.</p>
  
  <p>I mean, what, does <code>unset</code> magically not execute any assembly instructions whereas <code>$whatever = null;</code> does? The answer, as given, is about as useful as saying</p>
  
  <blockquote>
    <p>$whatever = null resets the buffer and the L1 cache whereas unset clears the buffer and resets the L2 cache. </p>
  </blockquote>
  
  <p>Techno mumbo jumbo doesn't constitute an answer.</p>