Example:
<code>
function hello() {
    ?>
    <script src="https://cdn.rawgit.com/google/code-prettify/master/loader/run_prettify.js"></script>
    <pre class="prettyprint lang-html linenums">
&lt;script type="text/javascript"&gt;
// Say hello world until the user starts questioning
// the meaningfulness of their existence.
function helloWorld(world) {
  for (var i = 42; --i &gt;= 0;) {
    alert('Hello ' + String(world));
  }
}
&lt;/script&gt;
&lt;style&gt;
p { color: pink }
b { color: blue }
u { color: "umber" }
&lt;/style&gt;
    </pre>
    <?php

}
</code>

the auto format add white space on each line  beginning inside <pre> tag
every time you call Format function.