PHP- Error with SQLSRV_FETCH_ASSOC & sqlsrv_fetch_array

我用来从excel中的sql服务器查询下载结果的代码。连接和查询工作正常，我已经正确安装了sqlsrv扩展。但是我仍然遇到这样的错误

"使用未定义的常数SQLSRV_FETCH_ASSOC - 假定 SQLSRV_FETCH_ASSOC'"
"警告：sqlsrv_fetch_array（） 预计参数 2 很长"

我认为问题出在SQLSRV_FETCH_ASSOC.任何帮助将不胜感激。

  function cleanData(&$str)
  {
    $str = preg_replace("/'t/", "''t", $str);
    $str = preg_replace("/'r?'n/", "''n", $str);
    if(strstr($str, '"')) $str = '"' . str_replace('"', '""', $str) . '"';
  }
  $serverName = "********"; 
$connectionInfo = array( "Database"=>"****", "UID"=>"***", "PWD"=>"*****");
$connect = sqlsrv_connect( $serverName, $connectionInfo);
  // filename for download
  $filename = "website_data_" . date('Ymd') . ".xls";
  header("Content-Disposition: attachment; filename='"$filename'"");
  header("Content-Type: application/vnd.ms-excel");
  $flag = false;
  $query="select * from business_partners ORDER BY 1 desc";
  $result = sqlsrv_query($connect, $query) or die('A error occured: ' . sqlsrv_errors());
  while(false !== ($row = sqlsrv_fetch_array($result,SQLSRV_FETCH_ASSOC))) 
  {
    if(!$flag) {
      // display field/column names as first row
      echo implode("'t", array_keys($row)) . "'r'n";
      $flag = true;
    }**strong text**
    array_walk($row, 'cleanData');
    echo implode("'t", array_values($row)) . "'r'n";
  }
  exit;