php preg_replace function

[eluser]basty_dread[/eluser]
Hi sophistry,
Thanks for helping on my topic preg_replace function
its really a big help..

i need your help again on this..
if you notice that it will surely match the word enclosed in <h2> tag..
is there a way it could exclude it from being replaced?

Code:

$string = "the quick brown fox jumps over the lazy dog, Brown Fox. <h2>The Brown Fox</h2>";
$find = "brown fox";
$save = preg_replace('/b('.$find.')b/ie', "str_replace(' ', 'x', '$1')", $string);
print_r($save);