PHP Progress bar breaks HTML>

I just implemented the progress bar described in "PHP 5 in Practice" by White and Eisenhamer on pp198ff.  The PHP code just echoes out a <style> section followed by a some div elements in the middle of the body section. What surprises me is that it's ok to stick a <style> ,,, </style> section in the middle of the body.  This seems to work fine but w3schools says for <style> at http://www.w3schools.com/tags/tag_style.asp :

The <style> element always goes inside the head section.

I'm just wondering how PHP gets around this. To make the bar go away when it reached completion I just echoed out:

echo "
	<style>
           #barbox {
		display:none;
	   }
	  #bar {
		display:none;
 	 }
	</style>
";

Select allOpen in new window

And that worked too.

Thanks for any input.