PHP 把数据写入CSV格式文件，并返回路径

$title = ['id', 'md5'];
$data = [
    [1,'kfbau5'],
    [2,'7FSn8u'],
    [3,'SzhBvL'],
    [4,'M0ynsf'],
    [5,'GgXyAV'],
    [6,'LHooy0'],
];
$fname = sprintf("csv导出.%s.csv", date('Ymd.His')) ;
$path = createCsv($title,$data,$fname);
var_dump( $path);

// 写入CSV
 function createCsv($title, $data, $fname)
{
    $file_path = $_SERVER['DOCUMENT_ROOT'] .'/'. $fname;
    $fp = fopen($file_path, 'a');

    //将数据编码转换成GBK格式
    //将数据格式化为CSV格式并写入到output流中
    mb_convert_variables('GBK', 'UTF-8', $title);
    fputcsv($fp, $title);
    foreach ($data as $row) {
        mb_convert_variables('GBK', 'UTF-8', $row);
        fputcsv($fp, $row);
    }
    fclose($fp);
    return $file_path;
}