How can PHP code be properly integrated with HTML to ensure correct output in a browser?

To properly integrate PHP code with HTML, you need to ensure that the PHP code is enclosed within `<?php ?>` tags and that the file has a `.php` extension. This allows the server to parse and execute the PHP code before sending the HTML output to the browser.

&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
    &lt;title&gt;PHP Integration&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
    &lt;h1&gt;Welcome &lt;?php echo &quot;User&quot;; ?&gt;&lt;/h1&gt;
&lt;/body&gt;
&lt;/html&gt;