title: PHP - For Loop incrementing
body: <p>This might looks dumb, but I have no idea how $a += 3; works.
  I can't figure out, for every answer I would be grateful </p>
  
  <pre><code>&lt;?php
  $a = 0;
  for ($i=0; $i&lt;5; $i++) { 
      $a += 3; // How this actually works
  }
  echo $a; // Echoing 15
  ?&gt;
  </code></pre>