我們常常會用到PHP過濾一些標簽的功能，比如過濾鏈接標簽、過濾script標簽等等，下面就介紹一下PHP過濾常用標簽的正則表達式代碼：
<?php
$str=preg_replace("/s+/", " ", $str); //過濾多余回車
$str=preg_replace("/<[ ]+/si","<",$str); //過濾<__("<"號后面帶空格)
$str=preg_replace("/<!–.*?–>/si","",$str); //注釋
$str=preg_replace("/<(!.*?)>/si","",$str); //過濾DOCTYPE
$str=preg_replace("/<(/?html.*?)>/si","",$str); //過濾html標簽
$str=preg_replace("/<(/?br.*?)>/si","",$str); //過濾br標簽
$str=preg_replace("/<(/?head.*?)>/si","",$str); //過濾head標簽
$str=preg_replace("/<(/?meta.*?)>/si","",$str); //過濾meta標簽
$str=preg_replace("/<(/?body.*?)>/si","",$str); //過濾body標簽
$str=preg_replace("/<(/?link.*?)>/si","",$str); //過濾link標簽
$str=preg_replace("/<(/?form.*?)>/si","",$str); //過濾form標簽
$str=preg_replace("/cookie/si","COOKIE",$str); //過濾COOKIE標簽
$str=preg_replace("/<(applet.*?)>(.*?)<(/applet.*?)>/si","",$str); //過濾applet標簽
$str=preg_replace("/<(/?applet.*?)>/si","",$str); //過濾applet標簽
$str=preg_replace("/<(style.*?)>(.*?)<(/style.*?)>/si","",$str); //過濾style標簽
$str=preg_replace("/<(/?style.*?)>/si","",$str); //過濾style標簽
$str=preg_replace("/<(title.*?)>(.*?)<(/title.*?)>/si","",$str); //過濾title標簽
$str=preg_replace("/<(/?title.*?)>/si","",$str); //過濾title標簽
$str=preg_replace("/<(object.*?)>(.*?)<(/object.*?)>/si","",$str); //過濾object標簽
$str=preg_replace("/<(/?objec.*?)>/si","",$str); //過濾object標簽
$str=preg_replace("/<(noframes.*?)>(.*?)<(/noframes.*?)>/si","",$str); //過濾noframes標簽
$str=preg_replace("/<(/?noframes.*?)>/si","",$str); //過濾noframes標簽
$str=preg_replace("/<(i?frame.*?)>(.*?)<(/i?frame.*?)>/si","",$str); //過濾frame標簽
$str=preg_replace("/<(/?i?frame.*?)>/si","",$str); //過濾frame標簽
$str=preg_replace("/<(script.*?)>(.*?)<(/script.*?)>/si","",$str); //過濾script標簽
$str=preg_replace("/<(/?script.*?)>/si","",$str); //過濾script標簽
$str=preg_replace("/javascript/si","Javascript",$str); //過濾javascript標簽
$str=preg_replace("/vbscript/si","Vbscript",$str); //過濾vbscript標簽
$str=preg_replace("/on([a-z]+)s*=/si","On\1=",$str); //過濾script標簽
$str=preg_replace("/&#/si","&＃",$str); //過濾script標簽，
?>