//ubbcode类
  class ubbcode{
  var $call_time=0;
  //可处理标签及处理函数对应表
  var $tags = array( //小写的标签 => 对应的处理函数
  'url' => '$this->url',
  'email' => '$this->email',
  'img' => '$this->img',
'flash' => '$this->flash',
'sound' => '$this->sound',
'black' => '$this->font_color',
'white' => '$this->font_color',
'red' => '$this->font_color',
'pink' => '$this->font_color',
'blue' => '$this->font_color',
'green' => '$this->font_color',
'olive' => '$this->font_color',
'navy' => '$this->font_color',
'gray'=> '$this->font_color',
'fuchsia' => '$this->font_color',
'yellow' => '$this->font_color',
'silver' => '$this->font_color',
'purple' => '$this->font_color',
'marquee' => '$this->simple',
  'b' => '$this->simple',
  'i' => '$this->simple',
  'u' => '$this->simple',
  'tt' => '$this->simple',
  's' => '$this->simple',
  'strike' => '$this->simple',
  'h1' => '$this->simple',
  'h2' => '$this->simple',
  'h3' => '$this->simple',
  'h4' => '$this->simple',
  'h5' => '$this->simple',
  'h6' => '$this->simple',
  'sup' => '$this->simple',
  'sub' => '$this->simple',
  'em' => '$this->simple',
  'strong' => '$this->simple',
  'code' => '$this->simple',
  'samp' => '$this->simple',
  'kbd' => '$this->simple',
  'var' => '$this->simple',
  'dfn' => '$this->simple',
  'cite' => '$this->simple',
  'small' => '$this->simple',
  'big' => '$this->simple',
  'blink' => '$this->simple'
  );
  //url裢接属性
  var $attr_url;
  //url合法性检查对象
  var $urlcheck;
function ubbcode($attr_url){
  $this->attr_url = ''.$attr_url;
  $this->urlcheck = new urlcheck();
  }
//对$str进行ubb编码解析
  function parse($str){
  $this->call_time++;
  $parse = ''.htmlencode($str);
$ret = '';
  while(true){
  $eregi_ret=eregi(\[[#]{0,1}[[:alnum:]]{1,7}\],$parse,$eregi_arr); //查找[xx]
  if(!$eregi_ret){
  $ret .= $parse;
  break; //如果没有，返回
  }
  $pos = @strpos($parse,$eregi_arr[0]);
  $tag_len=strlen($eregi_arr[0])-2;//标记长度
  $tag_start=substr($eregi_arr[0],1,$tag_len);
  $tag=strtolower($tag_start);
if((($tag==url) or ($tag==email) or ($tag==img) or ($tag==flash)) and ($this->call_time>1)){
  echo $this->call_time.
;
  return $parse;//如果不能是不能嵌套的标记，直接返回
  }
$parse2 = substr($parse,0,$pos);//标记之前
  $parse = substr($parse,$pos+$tag_len+2);//标记之后
  if(!isset($this->tags[$tag])){
  echo $tag_start
;
  $ret .= $parse2.'['.$tag_start.']';
  continue;//如果是不支持的标记
  }
//查找对对应的结束标记
  $eregi_ret=eregi(\[\/.$tag.\],$parse,$eregi_arr);
  if(!$eregi_ret){
  $ret .= $parse2.'['.$tag_start.']';
  continue;//如果没有对应该的结束标记
  }
  $pos=strpos($parse,$eregi_arr[0]);
  $value=substr($parse,0,$pos);//这是起止标记之间的内容
  $tag_end=substr($parse,$pos+2,$tag_len);
  $parse=substr($parse,$pos+$tag_len+3);//结束标记之后的内容
if(($tag!=url) and ($tag!=email) and ($tag!=img)and ($tag!=flash)){
  $value=$this->parse($value);
  }
$ret .= $parse2;
  eval('$ret .= '.$this->tags[$tag].'('.$tag_start.','.$tag_end.','.$value.');');
  }
  $this->call_time--;
  return $ret;
  }
function simple($start,$end,$value){
  return ''.$value.''.$end.'>';
  }
function url($start,$end,$value){
  $trim_value=trim($value);
  if (strtolower(substr($trim_value,0,7))!=http://)
  $trim_value=http://.$trim_value;
  if($this->urlcheck->check($trim_value)) return 'attr_url.'>'.$value.'';
  else return '['.$start.']'.$value.'[/'.$end.']';
  }
function email($start,$end,$value){
  if(emailcheck($value)) return ''.$value.'';
  else return '['.$start.']'.$value.'[/'.$end.']';
  }
function img($start,$end,$value){
  $trim_value=trim($value);
  if ((strtolower(substr($trim_value,0,7))!=http://) or ($this->urlcheck->check($trim_value)))
  return '';
  else return '['.$start.']'.$value.'[/'.$end.']';
  }
function flash($start,$end,$value){
  $trim_value=trim($value);
  if ((strtolower(substr($trim_value,0,7))!=http://) or ($this->urlcheck->check($trim_value)))
return '';
else return '['.$start.']'.$value.'[/'.$end.']';
  }
function sound($start,$end,$value){
  $trim_value=trim($value);
  if ((strtolower(substr($trim_value,0,7))!=http://) or ($this->urlcheck->check($trim_value)))
return ;
else return '['.$start.']'.$value.'[/'.$end.']';
  }
function font_color($start,$end,$value){
if(strstr(black|white|red|pink|blue|green|olive|navy|gray|fuchsia|yellow|silver|purple,$start))
return .$value.;
else return '['.$start.']'.$value.'[/'.$end.']';
  }
  }
//urlcheck.php
  class urlcheck{
  var $regex = array(//协议名(注意在这里必须写成小写) => 对应的正则表达式
  'ftp' => '$this->ftpurl',
  'file' => '$this->fileurl',
  'http' => '$this->httpurl',
  'https' => '$this->httpurl',
  'gopher' => '$this->gopherurl',
  'news' => '$this->newsurl',
  'nntp' => '$this->nntpurl',
  'telnet' => '$this->telneturl',
  'wais' => '$this->waisurl'
  );
var $lowalpha;
  var $hialpha;
  var $alpha;
  var $digit;
  var $safe;
  var $extra;
  var $national;
  var $punctuation;
  var $reserved;
  var $hex;
  var $escape;
  var $unreserved;
  var $uchar;
  var $xchar;
  var $digits;
var $urlpath;
  var $password;
  var $user;
  var $port;
  var $hostnumber;
  var $alphadigit;
  var $toplabel;
  var $domainlabel;
  var $hostname;
  var $host;
  var $hostport;
  var $login;
//ftp
  var $ftptype;
  var $fsegment;
  var $fpath;
  var $ftpurl;
//file
  var $fileurl;
//http,https
  var $search;
  var $hsegment;
  var $hpath;
  var $httpurl;
//gopher
  var $gopher_string;
  var $selector;
  var $gtype;
  var $gopherurl;
//news
  var $article;
  var $group;
  var $grouppart;
  var $newsurl;
//nntp
  var $nntpurl;
//telnet
  var $telneturl;
//wais
  var $wpath;
  var $wtype;
  var $database;
  var $waisdoc;
  var $waisindex;
  var $waisdatabase;
  var $waisurl;
function check($url){
  $pos = @strpos($url,':',1);
  if($pos  $prot = substr($url,0,$pos);
  if(!isset($this->regex[$prot])) return false;
  eval('$regex = '.$this->regex[$prot].';');
  return ereg('^'.$regex.'$',$url);
  }
function urlcheck(){
  $this->lowalpha = '[a-z]';
  $this->hialpha = '[a-z]';
  $this->alpha = '('.$this->lowalpha.'|'.$this->hialpha.')';
  $this->digit = '[0-9]';
  $this->safe = '[$.+_-]';
  $this->extra = '[*()\'!,]';
  $this->national = '([{}|\^~`]|\\[|\\])';
  $this->punctuation = '[#%]';
  $this->reserved = '[?;/:@&=]';
  $this->hex = '('.$this->digit.'|[a-fa-f])';
  $this->escape = '(%'.$this->hex.'{2})';
  $this->unreserved = '('.$this->alpha.'|'.$this->digit.'|'.$this->safe.'|'.$this->extra.')';
  $this->uchar = '('.$this->unreserved.'|'.$this->escape.')';
  $this->xchar = '('.$this->unreserved.'|'.$this->reserved.'|'.$this->escape.')';
  $this->digits = '('.$this->digit.'+)';
$this->urlpath = '('.$this->xchar.'*)';
  $this->password = '(('.$this->uchar.'|[?;&=]'.')*)';
  $this->user = '(('.$this->uchar.'|[?;&=]'.')*)';
  $this->port = $this->digits;
  $this->hostnumber = '('.$this->digits.'.'.$this->digits.'.'.$this->digits.'.'.$this->digits.')';
  $this->alphadigit = '('.$this->alpha.'|'.$this->digit.')';
  $this->toplabel = '('.$this->alpha.'|('.$this->alpha.'('.$this->alphadigit.'|-)*'.$this->alphadigit.'))';
  $this->domainlabel = '('.$this->alphadigit.'|('.$this->alphadigit.'('.$this->alphadigit.'|-)*'.$this->alphadigit.'))';
  $this->hostname = '(('.$this->domainlabel.'\\.)*'.$this->toplabel.')';
  $this->host = '('.$this->hostname.'|'.$this->hostnumber.')';
  $this->hostport = '('.$this->host.'(:'.$this->port.')?)';
  $this->login = '(('.$this->user.'(:'.$this->password.')?@)?'.$this->hostport.')';
$this->ftptype = '[aidaid]';
  $this->fsegment = '(('.$this->uchar.'|[?:@&=])*)';
  $this->fpath = '('.$this->fsegment.'(/'.$this->fsegment.')*)';
  $this->ftpurl = '([ff][tt][pp]://'.$this->login.'(/'.$this->fpath.'(;[tt][yy][pp][ee]='.$this->ftptype.')?)?)';
$this->fileurl = '([ff][ii][ll][ee]://('.$this->host.'|[ll][oo][cc][aa][ll][hh][oo][ss][tt])?/'.$this->fpath.')';
$this->search = '(('.$this->uchar.'|[;:@&=])*)';
  $this->hsegment = '(('.$this->uchar.'|[;:@&=])*)';
  $this->hpath = '('.$this->hsegment.'(/'.$this->hsegment.')*)';
  $this->httpurl = '([hh][tt][tt][pp][ss]?://'.$this->hostport.'(/'.$this->hpath.'([?]'.$this->search.')?)?)';
$this->gopher_string = '('.$this->xchar.'*)';
  $this->selector = '('.$this->xchar.'*)';
  $this->gtype = $this->xchar;
  $this->gopherurl = '([gg][oo][pp][hh][ee][rr]://'.$this->hostport.'(/('.$this->gtype.'('.$this->selector.'(%09'.$this->search.'(%09'.$this->gopher_string.')?)?)?)?)?)';
$this->article = '(('.$this->uchar.'|[;/?:&=])+@'.$this->host.')';
  $this->group = '('.$this->alpha.'('.$this->alpha.'|'.$this->digit.'|[-.+_])*)';
  $this->grouppart = '([*]|'.$this->group.'|'.$this->article.')';
  $this->newsurl = '([nn][ee][ww][ss]:'.$this->grouppart.')';
$this->nntpurl = '([nn][nn][tt][pp]://'.$this->hostport.'/'.$this->group.'(/'.$this->digits.')?)';
$this->telneturl = '([tt][ee][ll][nn][ee][tt]://'.$this->login.'/?)';
$this->wpath = '('.$this->uchar.'*)';
  $this->wtype = '('.$this->uchar.'*)';
  $this->database = '('.$this->uchar.'*)';
  $this->waisdoc = '([ww][aa][ii][ss]://'.$this->hostport.'/'.$this->database.'/'.$this->wtype.'/'.$this->wpath.')';
  $this->waisindex = '([ww][aa][ii][ss]://'.$this->hostport.'/'.$this->database.'[?]'.$this->search.')';
  $this->waisdatabase = '([ww][aa][ii][ss]://'.$this->hostport.'/'.$this->database.')';
  $this->waisurl = '('.$this->waisdatabase.'|'.$this->waisindex.'|'.$this->waisdoc.')';
  }
  }
function htmlencode($str){
  $str = (string)$str;
$ret = '';
  $len = strlen($str);
  $nl = false;
  for($i=0;$i  $chr = $str[$i];
  switch($chr){
  case '  $ret .= '  $nl = false;
  break;
  case '>':
  $ret .= '>';
  $nl = false;
  break;
  case '':
  $ret .= '';
  $nl = false;
  break;
  case '&':
  $ret .= '&';
  $nl = false;
  break;
  /*
  case ' ':
  $ret .= ' ';
  $nl = false;
  break;
  */
  case chr(9):
  $ret .= '    ';
  $nl = false;
  break;
/*
  case chr(10):
  if($nl) $nl = false;
  else{
  $ret .= '
';
  $nl = true;
  }
  break;
case chr(13):
  if($nl) $nl = false;
  else{
  $ret .= '
';
  $nl = true;
  }
  break;
*/
  default:
  $ret .= $chr;
  $nl = false;
  break;
  }
  }
return $ret;
  }
function htmlencode4textarea($str){
  $str = (string)$str;
$ret = '';
  $len = strlen($str);
  for($i=0;$i  $chr = $str[$i];
  switch($chr){
  case '  $ret .= '  break;
  case '>':
  $ret .= '>';
  break;
  case '':
  $ret .= '';
  break;
  case '&':
  $ret .= '&';
  break;
  case ' ':
  $ret .= ' ';
  break;
  case chr(9):
  $ret .= '    ';
  break;
  default:
  $ret .= $chr;
  break;
  }
  }
return $ret;
  }
function emailcheck($email){
  $ret=false;
  if(strstr($email, '@') && strstr($email, '.')){
  if(eregi(^([_a-z0-9]+([\\._a-z0-9-]+)*)@([a-z0-9]{2,}(\\.[a-z0-9-]{2,})*\\.[a-z]{2,3})$, $email)){
  $ret=true;
  }
  }
  return $ret;
  }
function str2url($path){
  return eregi_replace(%2f,/,urlencode($path));
  }
?>
--------------------------
说明：在网上找了半天发现全是何志强的那段代码，我也就拿来改了一下用上了。其中加入了一部分自己的内容，只是还不太清楚如何规定图片等元素的大小。我曾经把 function img($start,$end,$value){
  $trim_value=trim($value);
  if ((strtolower(substr($trim_value,0,7))!=http://) or ($this->urlcheck->check($trim_value)))
  return '';
  else return '['.$start.']'.$value.'[/'.$end.']';
  }
改为：
function img($start,$end,$value){
  $trim_value=trim($value);
  if ((strtolower(substr($trim_value,0,7))!=http://) or ($this->urlcheck->check($trim_value)))
{
$pisces=explode( ,$start);
if(!is_int($pisces[1]) || !!is_int($pisces[2]))
return '';
else
return '';
}
else return '['.$start.']'.$value.'[/'.$end.']';
  }
但由于对前面的正则表达式不熟悉没成功。