preg_replace to remove line breaks between two tags?

I currently have some custom tags, similar to BBCode, to be used for comments on my site. I'm trying to create a [nobr] tag (note: I know the no break tag will work in many major browsers, but it's deprecated, so I'm trying to be compliant) to remove all line breaks between the opening and closing tag.

The idea is that if I encounter the [nobr] tag, I need to remove all line breaks between the opening and closing tags. Here's the best I could come up with, but it doesn't work. I can't think of anything else! Can anyone shed some light and help me out.  I could be way off here...

Note: the new part I'm working on is where you see the before, during, after. The other part of the function is for reference of what I'm working with thus far.

function BbToHtml($str) {

$pattern = array (
          "/\[b\](.+)\[\/b\]/Usi",
          "/\[i\](.+)\[\/i\]/Usi",
          "/\[u\](.+)\[\/u\]/Usi",
          "/\[color=(\#[0-9A-F]{6}|[a-z]+)\](.*)\[\/color\]/Usi",
          "/\[size=(.*)\](.*)\[\/size\]/Usi",
          "/\[img=(.*)\](.*)\[\/img\]/Usi",
          "/\[url=(.*)\](.+)\[\/url\]/Usi",
          );

$replace = array (
          "<strong>\\1</strong>",
          "<em>\\1</em>",
          "<u>\\1</u>",
          "<span style=\"color:\\1\">\\2</span>",
          "<img src='\\1' alt='\\2' border=\"0\"/>",
          "<a href='\\1' target='_new'>\\2</a>",
          );

$before=preg_replace("(.*)/\[nobr\](.*)\[\/nobr](.*)/Usie", "\\1", $str);
$during=preg_replace("(.*)/\[nobr\](.*)\[\/nobr](.*)/Usie", "\\2", $str);
$after=preg_replace("(.*)/\[nobr\](.*)\[\/nobr](.*)/Usie", "\\3", $str);

if($during != "") {
  $during=str_replace("\r\n","",$during);
  $str=$before.$during.$after;
}

$str=nl2br($str);
$str = preg_replace($pattern,$replace,$str);
return $str;
}

Dug in and figured it out...whew. For any poor souls out there: Make sure to do this AFTER the nl2br function.

$str = preg_replace("/\[nobr\](.*?)\[\/nobr\]/esiU", "stripslashes(preg_replace('/<br(\s)?(?(1)\/)>/i', '', '\\1'))", $str);