LOL this is the FOURTH time I've answered this question this week!
<?php
$string_with_php_code_in_it = " this is my html <?php print ("this is my php code "); ?> this is the rest of my html ";
eval (" ?> " . $string_with_php_code_in_it . " <?php ");
?>
You should be able to figure out the rest on your own.