PHP exports csv files, leading 0 instances can be exported

//导出csv格式文件 $data数据 $title_arr标题 $file_name文件名
function exportCsv($data,$title_arr,$file_name=''){
  ini_set("max_execution_time", "3600");

  $csv_data = '';
  /** 标题 */
  $nums = count($title_arr);

  for ($i = 0; $i < $nums - 1; ++$i) {
    $csv_data .= &#39;"&#39; . $title_arr[$i] . &#39;",&#39;;
  }
  if ($nums > 0) {
    $csv_data .= &#39;"&#39; . $title_arr[$nums - 1] . "\"\r\n";
  }

  foreach ($data as $k => $row) {
    foreach ($row as $key => $r){

      $row[$key] = str_replace("\"", "\"\"", $r);

      $csv_data .= "\"\t" . $row[$key] . &#39;",&#39;;
    }

    $csv_data .= &#39;"&#39; . $row[$nums - 1] . "\"\r\n";
    unset($data[$k]);
  }
  $csv_data = mb_convert_encoding($csv_data, "cp936", "UTF-8");
  $file_name = empty($file_name) ? date(&#39;Y-m-d-H-i-s&#39;, time()) : $file_name;
  if (strpos($_SERVER[&#39;HTTP_USER_AGENT&#39;], "MSIE")) { // 解决IE浏览器输出中文名乱码的bug
    $file_name = urlencode($file_name);
    $file_name = str_replace(&#39;+&#39;, &#39;%20&#39;, $file_name);
  }
  $file_name = $file_name . &#39;.csv&#39;;
  header(&#39;Content-Type: application/download&#39;);
  header("Content-type:text/csv;");
  header("Content-Disposition:attachment;filename=" . $file_name);
  header(&#39;Cache-Control:must-revalidate,post-check=0,pre-check=0&#39;);
  header(&#39;Expires:0&#39;);
  header(&#39;Pragma:public&#39;);
  echo $csv_data;
  exit();
}