title: PHP addition/subtraction of letters
body: <p>I have the following test code:</p>
  
  <pre><code>&lt;?php
  
  $letter = 'A';
  $letter++;
  $letter++;
  
  echo $letter.'&lt;br&gt;';  // C
  
  $letter++;
  $letter++;
  $letter++;
  
  echo $letter.'&lt;br&gt;';  // F
  
  // how to add plus 3 letters
  // so that 
  // $letter + 3 =&gt; I
  </code></pre>
  
  <p>As shown here by using <code>$letter++</code> or <code>$letter--</code> I can go up or down a character. Is there a way I can do something like  <code>$letter + 3</code> so it adds up 3 letters.</p>
  
  <p>I know I can make a function with a loop which will add a char by char and at the end I will get the result. But is there a better way?</p>