PHP string replace inside string problem

[RemoteBiscuit]

Well my problem is simple yet complex
Basically I have a custom forum system using PHP, and I just tried adding a "[dhtml] HTML HERE [/dhtml]" function, but whatever I try nothing works.
Ideally I need a script that replaces "&lt;" with "<" and "&gt;" with ">", but only inside the "[dhtml] [/dhtml]" tags.
Here is what I have tried:

$toreplace = "[dhtml]<b>This is bold sample text</b>[/dhtml]"
$replmeDhtml = "/\[dhtml\](.*?)\[\/dhtml\]/";
$replyouDhtml = "[dhtml]\\1[/dhtml]";
$replyouDhtml = str_replace("&lt;","<",$replyuDhtml);
$replyouDhtml = str_replace("&gt;",">",$replyuDhtml);
$toreplace = preg_replace($replmeDhtml,$replyouDhtml,$toreplace);
echo $toreplace;

But nothing.

Any ideas?

[Weedpacket]

Consider using [man]preg_replace_callback[/man]. Match the bit between the metatags and pass it to another function which does the de-entification.