/**
 * 匯出CSV格式
 * @param $headArr 匯出內容表頭
 * @param $exportData 匯出資料內容
 * @param $title 匯出的標題
 * @createTime:2021-6-22 11:50
 * @author:LTTT
 */
public function exportCsv($headArr, $exportData, $title = '')
{
    if (empty($headArr) || empty($exportData)) {
        throw new \Exception("表頭或者內容不能為空");
    }
    if (empty($title)) {
　　　　　// 標題根據自己需要生成
        $title = time();
    }
    $total = count($exportData);
    header("Content-type:application/vnd.ms-excel");
    header("Content-Disposition:filename=" . iconv("UTF-8", "GB18030", $title) . ".csv");
    $fp = fopen('php://output', 'a');
    $headName = array_keys($headArr);
    $headValue = array_values($headArr);
    fputcsv($fp, $headValue);
    $size = 2000;
    $groupNum = ceil($total / $size);
    for ($i = 0; $i <= $groupNum; $i++) {
        $exportDataTemp = array_slice($exportData, $size * $i, $size);
        foreach ($exportDataTemp as $item) {
            $rows = array();
            foreach ($headName as $name) {
                $rows[] = $item[$name];
            }
            fputcsv($fp, $rows);
        }
        ob_flush();
        flush();
    }
    die;
}