php csv导出Mac和Windows系统异常

Question

csv导出代码：

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;
    }

在Mac系统中，打开时只有一列。

在Windows系统中，打开时有四列。

你能告诉我如何修改代码吗？它可以与多个系统兼容吗？