我们常常会用到PHP过滤一些标签的功能，比如过滤链接标签、过滤script标签等等，下面就介绍一下PHP过滤常用标签的正则表达式代码：

<?php

$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

$str=preg_replace("/<(/?br.*?)>/si","",$str); //过滤br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

$str=preg_replace("/<(applet.*?)>(.*?)<(/applet.*?)>/si","",$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javascript标签

$str=preg_replace("/vbscript/si","Vbscript",$str); //过滤vbscript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，

?>