function ubb($Text) { 
  $Text=htmlspecialchars($Text); 
  $Text=ereg_replace("\r\n","br>",$Text); 
  $Text=ereg_replace("\r","br>",$Text); 
  $Text=nl2br($Text); 
  $Text=preg_replace("/\\t/is","  ",$Text); 
  $Text=preg_replace("/\[h1\](.+?)\[\/h1\]/is","h1>\\1/h1>",$Text); 
  $Text=preg_replace("/\[h2\](.+?)\[\/h2\]/is","h2>\\1/h2>",$Text); 
  $Text=preg_replace("/\[h3\](.+?)\[\/h3\]/is","h3>\\1/h3>",$Text); 
  $Text=preg_replace("/\[h4\](.+?)\[\/h4\]/is","h4>\\1/h4>",$Text); 
  $Text=preg_replace("/\[h5\](.+?)\[\/h5\]/is","h5>\\1/h5>",$Text); 
  $Text=preg_replace("/\[h6\](.+?)\[\/h6\]/is","h6>\\1/h6>",$Text); 

  $Text=preg_replace("/\[url\](http:\/\/.+?)\[\/url\]/is","a href=\\1>\\1/a>",$Text); 
  $Text=preg_replace("/\[url\](.+?)\[\/url\]/is","a href=\"http://\\1\">http://\\1/a>",$Text); 
  $Text=preg_replace("/\[url=(http:\/\/.+?)\](.*)\[\/url\]/is","a href=\\1>\\2/a>",$Text); 
  $Text=preg_replace("/\[url=(.+?)\](.*)\[\/url\]/is","a href=http://\\1>\\2/a>",$Text); 

  $Text=preg_replace("/\[img\](.+?)\[\/img\]/is","img src=\\1>",$Text); 
  $Text=preg_replace("/\[color=(.+?)\](.+?)\[\/color\]/is","font color=\\1>\\2/font>",$Text); 
  $Text=preg_replace("/\[size=(.+?)\](.+?)\[\/size\]/is","font size=\\1>\\2/font>",$Text); 
  $Text=preg_replace("/\[sup\](.+?)\[\/sup\]/is","sup>\\1/sup>",$Text); 
  $Text=preg_replace("/\[sub\](.+?)\[\/sub\]/is","sub>\\1/sub>",$Text); 
  $Text=preg_replace("/\[pre\](.+?)\[\/pre\]/is","pre>\\1/pre>",$Text); 
  $Text=preg_replace("/\[email\](.+?)\[\/email\]/is","a href=\\1>\\1/a>",$Text); 
  $Text=preg_replace("/\[i\](.+?)\[\/i\]/is","i>\\1/i>",$Text); 
  $Text=preg_replace("/\[b\](.+?)\[\/b\]/is","b>\\1/b>",$Text); 
  $Text=preg_replace("/\[quote\](.+?)\[\/quote\]/is","blockquote>font size='2' face='Courier New'>quote:/font>hr>\\1hr>/blockquote>", $Text); 
  $Text=preg_replace("/\[code\](.+?)\[\/code\]/is","blockquote>font size='2' face='Courier New'>code:/font>hr color='lightblue'>i>\\1/i>hr color='lightblue'>/blockquote>", $Text); 
  $Text=preg_replace("/\[sig\](.+?)\[\/sig\]/is","div style='text-align: left; color: darkgreen; margin-left: 5%'>br>br>--------------------------br>\\1br>--------------------------/div>", $Text); 
return $Text; 
} 
function str($msg){
  global $admin;
  if(!$admin[html]) $msg=htmlspecialchars($msg);
  if($admin[ubb]) $msg=ubb($msg);
  $msg=nl2br($msg); #处理message
  $msg= str_replace("\n","",$msg); #处理message
  $msg= str_replace("\r","",$msg); #处理message
  return $msg;
}
function error($msg){
global $admin;
?>

中的
$Text=preg_replace("/\[h2\](.+?)\[\/h2\]/is","h2>\\1/h2>",$Text); 

里面的 ("/\[h2](.+?)\[\/h2]/is","h2>\\1/h2>",$text)

/\[h2](.+?)\[\/h2]/is  转化成 h2>\\1/h2>

/\[h2](.+?)\[\/h2]/is  里面的 这些"/\(.+?)\&;"之类的符号是怎么看的?是什么意思?
______________________________________________________________________________________________

\是转意，\本身是特殊符号，如果要作为普通字符就要用\来转意，就是说\\表示()也是特殊符号，所以要用\转意