How to get user IP address in PHP

/** * 用来获取用户的ip地址方法 * @return array|false|string 用户的ip地址 */ public function getUserIP() { if(getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknow")){ $ip = getenv("HTTP_CLIENT_IP"); }else if(getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknow")){ $ip = getenv("HTTP_X_FORWARDED_FOR"); }else if(getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknow")){ $ip = getenv("REMOTE_ADDR"); }else if(isset($_SERVER["REMOTE_ADDR"]) && $_SERVER["REMOTE_ADDR"] && strcasecmp($_SERVER["REMOTE_ADDR"],"unknow")){ $ip = $_SERVER["REMOTE_ADDR"]; }else{ $ip = "unknow"; } return $ip; }