php csv在Mac和Windows系统之间异常导出

Question

csv export code：

public function export_csv(){
        if(($id = $this->get_input('resultId')) == '') {
            $this->msg('error');
        }
        $result = call_mod_func('admin/activity_mod', 'get_result', array($id));
        $str = "name,email,mobile,tel" . PHP_EOL;
        $str = iconv('utf-8', 'gb2312', $str);  

        foreach($result['rows'] as $row) {
            $name = iconv('utf-8', 'gb2312', $row['name']);
            $email = $row['email'];
            $mobile = $row['mobile'];
            $weixinid = iconv('utf-8', 'gb2312', $row['weixinid']);

            $str .= $name . ',' . $email . ',' . $mobile . ',' . $weixinid . PHP_EOL;
        }

        $filename = date('Ymd', gettime()) . '.csv';  

        header("Content-type:text/csv");
        header("Content-Disposition:attachment;filename=".$filename);
        header('Cache-Control:must-revalidate,post-check=0,pre-check=0');
        header('Expires:0');
        header('Pragma:public');
        echo $str;
    }

In Mac system, when open it only has one column.

In Windows system, when open it has four column.

Could you tell me how to modify the code? Can it be compatible with multiple systems?