title: please explain following out put
body: <p>Here, I have following code it getting output like 21,21. How 21 value comes in $a</p>
  
  <pre><code> $a = '1';
   $b = &amp;$a;
   $b = "2$b";
   echo $a.", ".$b;
  </code></pre>
  
  <p>Output</p>
  
  <pre><code> 21,21
  </code></pre>