1.strip_tags(剝去字符串中的HTML標簽)  
strip_tags()函數剝去字符串中的HTML、XML以及PHP的標簽。  


2.字符串替換  

str_replace(array(" "," ","\t","\r\n","\r","\n"),array("","","","","","")


3.利用正則表達式(效率稍微低一些)  

$str=preg_replace("/\s+/","",$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  
$str=preg_replace("/<(\/?head.*?)>/si","",$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script標簽  
$str=preg_replace("/vbscript/si","Vbscript",$str);//過濾script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,如javAsCript:alert(