sqli_anti(s57)

public function __construct()
    {
        $dissalow_useragent = ['sqlmap','bot','curl'];
        if(preg_match("/".implode("|",$dissalow_useragent)."/",$_SERVER['HTTP_USER_AGENT']))
        {
            exit('Error.');
        }
        public function filter_xss($filter)
        {
        $str = addslashes(stripslashes(strip_tags(htmlspecialchars($filter))));
        return $str;
        }
        public function filter_sqli($id)
        {
        $tolak = ['union','select','group','concat','order by'];
        $p = str_replace(implode("|",$tolak),"",$id);
        $p = abs($id);
        return $p;
        }
        function filter_ua(){
        $useragent = array("sqlmap","curl","wget");
        $getuseragent = $_SERVER['HTTP_USER_AGENT'];
        if(preg_match("/".implode("|",$useragent)."/",$getuseragent)){
        header('HTTP/1.0 404 Not Found');
        exit;
        }
    }
    }