    public static function connect ($dbhost=DB_HOST, $dbuser=DB_USER, 
        $dbpass=DB_PASS, $dbname=DB_NAME) {
        
        self::$mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname);
        
        if (self::$mysqli->connect_error) {
            return false;
        }else{
            return true;
        }

    }

The software constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component.