php data array echo to excel file

<?PHP
  $data = array(
    array("firstname" => "Mary", "lastname" => "Johnson", "age" => 25),
    array("firstname" => "Amanda", "lastname" => "Miller", "age" => 18),
    array("firstname" => "James", "lastname" => "Brown", "age" => 31),
    array("firstname" => "Patricia", "lastname" => "Williams", "age" => 7),
    array("firstname" => "Michael", "lastname" => "Davis", "age" => 43),
    array("firstname" => "Sarah", "lastname" => "Miller", "age" => 24),
    array("firstname" => "Patrick", "lastname" => "Miller", "age" => 27)
  );

  function cleanData(&$str)
  {
    $str = preg_replace("/\t/", "\\t", $str);
    $str = preg_replace("/\r?\n/", "\\n", $str);
    if(strstr($str, '"')) $str = '"' . str_replace('"', '""', $str) . '"';
  }

  // file name for download
  $filename = "website_data_" . date('Ymd') . ".xls";

  header("Content-Disposition: attachment; filename=\"$filename\"");
  header("Content-Type: application/vnd.ms-excel");

  $flag = false;
  foreach($data as $row) {
    if(!$flag) {
      // display field/column names as first row
      echo implode("\t", array_keys($row)) . "\n";
      $flag = true;
    }
    array_walk($row, 'cleanData');
    echo implode("\t", array_values($row)) . "\n";
  }

  exit;
?>