第一种

$str=preg_replace("/<s*imgs+[^>]*?srcs*=s*('|")(.*?)\1[^>]*?/?s*>/i","", $str); //过滤img标签  
   
$str=preg_replace("/s+/","", $str); //过滤多余回车  
   
$str=preg_replace("/<[ ]+/si","<",$str); //过滤<__("<"号后面带空格)  
   
$str=preg_replace("/<!--.*?-->/si","",$str); //注释  
   
$str=preg_replace("/<(!.*?)>/si","",$str); //过滤DOCTYPE  
   
$str=preg_replace("/<(/?html.*?)>/si","",$str); //过滤html标签  
   
$str=preg_replace("/<(/?head.*?)>/si","",$str); //过滤head标签  
   
$str=preg_replace("/<(/?meta.*?)>/si","",$str); //过滤meta标签  
   
$str=preg_replace("/<(/?body.*?)>/si","",$str); //过滤body标签  
   
$str=preg_replace("/<(/?link.*?)>/si","",$str); //过滤link标签  
   
$str=preg_replace("/<(/?form.*?)>/si","",$str); //过滤form标签  
   
$str=preg_replace("/cookie/si","COOKIE",$str); //过滤COOKIE标签  
// http://www.manongjc.com/article/1345.html  
$str=preg_replace("/<(applet.*?)>(.*?)<(/applet.*?)>/si","",$str); //过滤applet标签  
   
$str=preg_replace("/<(/?applet.*?)>/si","",$str); //过滤applet标签  
   
$str=preg_replace("/<(style.*?)>(.*?)<(/style.*?)>/si","",$str); //过滤style标签  
   
$str=preg_replace("/<(/?style.*?)>/si","",$str); //过滤style标签  
   
$str=preg_replace("/<(title.*?)>(.*?)<(/title.*?)>/si","",$str); //过滤title标签  
   
$str=preg_replace("/<(/?title.*?)>/si","",$str); //过滤title标签  
   
$str=preg_replace("/<(object.*?)>(.*?)<(/object.*?)>/si","",$str); //过滤object标签  
   
$str=preg_replace("/<(/?objec.*?)>/si","",$str); //过滤object标签  
   
$str=preg_replace("/<(noframes.*?)>(.*?)<(/noframes.*?)>/si","",$str); //过滤noframes标签  
   
$str=preg_replace("/<(/?noframes.*?)>/si","",$str); //过滤noframes标签  
   
$str=preg_replace("/<(i?frame.*?)>(.*?)<(/i?frame.*?)>/si","",$str); //过滤frame标签  
   
$str=preg_replace("/<(/?i?frame.*?)>/si","",$str); //过滤frame标签  
   
$str=preg_replace("/<(script.*?)>(.*?)<(/script.*?)>/si","",$str); //过滤script标签  
   
$str=preg_replace("/<(/?script.*?)>/si","",$str); //过滤script标签  
   
$str=preg_replace("/javascript/si","Javascript",$str); //过滤script标签  
   
$str=preg_replace("/vbscript/si","Vbscript",$str); //过滤script标签  
   
$str=preg_replace("/on([a-z]+)s*=/si","On\1=",$str); //过滤script标签  
   
$str=preg_replace("/&#/si","&＃",$str); //过滤script标签

第二种

function delhtml($str){  //清除html标签  
$st=-1; //开始  
$et=-1; //结束  
$stmp=array();  
$stmp[]=" ";  
$len=strlen($str);  
for($i=0;$i<$len;$i++){  
  $ss=substr($str,$i,1);  
  if(ord($ss)==60){ //ord("<")==60 http://www.manongjc.com/article/1345.html  
  $st=$i;  
  }  
  if(ord($ss)==62){ //ord(">")==62  
  $et=$i;  
  if($st!=-1){  
   $stmp[]=substr($str,$st,$et-$st+1);  
  }  
  }  
}  
$str=str_replace($stmp,"",$str);  
return $str;  
}

第三种

function clear_html_label($html)   
{   
$search = array ("'<script[^>]*?>.*?</script>'si", "'<[/!]*?[^<>]*?>'si", "'([rn])[s]+'", "'&(quot|#34);'i", "'&(amp|#38);'i", "'&(lt|#60);'i", "'&(gt|#62);'i", "'&(nbsp|#160);'i", "'&(iexcl|#161);'i", "'&(cent|#162);'i", "'&(pound|#163);'i", "'&(copy|#169);'i", "'&#(d+);'e");   
$replace = array ("", "", "1", """, "&", "<", ">", " ", chr(161), chr(162), chr(163), chr(169), "chr(1)");  
return preg_replace($search, $replace, $html);   
}