title: Use of ob_start() and ob_get_clean()
body: <p>I usually code like this:</p>
  
  <pre><code>$output .= 'custom code';
      $output .= 'another line of custom code';
  $output .= 'more code';     
  
  return $output;
  </code></pre>
  
  <p>Now I want to use <code>ob_start()</code>, <code>ob_get_contents()</code> and <code>ob_get_clean()</code>. 
  What's the most effective way to use it inside my example?</p>