You can use Iframes for this:
<iframe src="http://example.com/form.php" name="myform"> // or src="path/to/your/form.php"
// the content of your Iframe goes here...
</iframe>
http://www.quackit.com/html_5/tags/html_iframe_tag.cfm
http://webdesign.about.com/od/iframes/a/html5-iframe-attributes.htm