You are probably aware of this, but just drop out of PHP code completely..
PHP Code:
<?php
some.php.code.here();
?>
<html>
here is the html code
the value of $variable is <?=$variable?>
</html>
<?
more.php.code.here();
?>
And use the php echo() shortcut syntax to return the values of variables ie. <?=$somevariable?> (just enclose the variable inside of <?= ... ?>
Note to use this echo() shortcut you must have the short_open_tag configuration directive enabled.
I do not know of any specific function that would allow raw html code to be echo'd back to the browser. This is just the way this type of embedded code forces us to work i think!