谷歌：
 "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.86 Safari/537.36"

火狐：
 "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:53.0) Gecko/20100101 Firefox/53.0" 

IE:
"Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko" 

public function isIE() { 
	$isIE = strpos($_SERVER[‘HTTP_USER_AGENT‘],"Triden");
	return $isIE;	
}