php正则过滤html标签、空格、换行符的代码(附说明)

代码如下：

$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 

$str=preg_replace("/<(applet.*?)>(.*?)<(\/applet.*?)>/si","",$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，如javAsCript:alert(