title: PHP creates new instance when pushing element
body: <p>Why does PHP create a new array when I push an element?</p>
  
  <pre><code>$a = array();
  $b = $a;
  
  $b[] = "Hello!";
  echo count($a);
  echo count($b);
  </code></pre>
  
  <p>Here you would expect the count for $a and $b to be equal, but they are not.</p>