title: Differences in concatenating strings
body: <p>What are the differences in the results of these three strings:</p>
  
  <ol>
  <li><p><code>echo "Hello" . "World! &lt;br /&gt;";</code></p></li>
  <li><p><code>echo "Hello"; echo "World!" , "&lt;br /&gt;";</code></p></li>
  <li><p><code>echo "Hello" , "World!" , "&lt;br /&gt;";</code></p></li>
  </ol>
  
  <p>Is there any preferred way to concatenate strings or are they all acceptable?</p>