title: Key of null variable equals null not error
body: <p>We've got variable that for some reason we think would be an array, but it happens to be null. </p>
  
  <p><code>$var = null</code></p>
  
  <p>We try to get a value from this variable. </p>
  
  <p><code>$value = $var['key']</code></p>
  
  <p>This doesn't throw an error, my intuition is that it would though. What instead happens is that $value is now also null. Is there a particular reason that the above line doesn't throw an error?</p>