title: How does the bitwise operator XOR ('^') work?
body: <p>I'm a little confused when I see the output of following code:</p>
  
  <pre><code>$x = "a";
  $y = "b";
  $x ^= $y;
  $y ^= $x;
  $x ^= $y;
  echo $x; //Got b
  echo $y; //Got a
  </code></pre>
  
  <p>How does the operator <code>^</code> work here?</p>