The Bakery Everything CakePHP

For this article I'll assume that you need a basic output: one or more sheets with each one row of field names (header) and multiple rows of data. I have adapted PEAR's class to let it function without the other PEAR libraries. You can download my version at http://webdesign.janenanneriet.nl/excel_writer.zip. You also need PEAR's OLE class, which I have also adapted (download at http://webdesign.janenanneriet.nl/ole.zip).

Preparation

Vendor classes

Extract the two zip files to your vendors directory. You might want to change the error handling in these files if you want your user to generate Excel files on-the-fly. I have namely substituted the PEAR Error class with PHP's native trigger_error() function. You can change all calls to trigger_error() to use Cake's Error class.

Helper

In order to generate the Excel file, we'll use a Helper class. This idea is also used in the article on PDF generation (http://bakery.cakephp.org/articles/view/218). The helper facilitates in the creation of several default cell formatting parameters (text, date, datetime, numbers and money). It sets the default properties for text style and layout (font, size, bold, etc.) and facilitates in converting dates and times to the Excel format. The helper file should be called excel.php.

Helper Class:

Download code <?php 
set_time_limit(10); // Set maximum execution time to 10 seconds.
error_reporting(E_ALL ^E_NOTICE); // Notice errors break the Excel file format.

define('TEXT_FORMAT',     0);
define('NUM_FORMAT',      1);
define('MONEY_FORMAT',    2);
define('DATE_FORMAT',     3);
define('TIME_FORMAT',     4);
define('DATETIME_FORMAT', 5);

vendor('excel_writer/ExcelWriter');
vendor('ole/OleRoot');
vendor('ole/OleFile');

class excelHelper extends ExcelWriter {

  var $workbook;
  var $worksheets = array();
  var $formats    = array();
  
  var $font   = 'Arial';
  var $size   = 10;
  var $align  = 'left';
  var $valign = 'vcenter';
  var $bold   = 0;
  var $italic = 0;

  /**
   * Creates the necessary objects and a temporary Excel file. Sets the
   * directory for temporary file creation and sets the version to
   * Excel 97 (support UTF-8).
   *
   * @param string  $filename  Name of the downloadable file
   */
  function excelHelper($filename = 'data.xls') {
    $this->workbook =& new ExcelWriter();
    $this->workbook->setTempDir(TMP."cache");

    $this->workbook->setVersion(8); // Set workbook to Excel 97 (for UTF-8 support)
  }

  /**
   * Returns an array with parameters that can be used to create an XF
   * formatting array. Default values are overridden when specified in
   * the parameter array.
   *
   * @param  array  $params  Array with parameters to define formatting.
   *                         Keys refer to the style properties.
     * @return string          Formatting array.
   */
  function _getFormatArray($params = NULL) {
    $temp = array('font'   => $this->font,
                  'size'   => $this->size,
                  'bold'   => $this->bold,
                  'italic' => $this->italic,
                  'align'  => $this->align,
                  'valign' => $this->valign);
    if(isset($params)) {
      foreach($params as $key => $value) {
        $temp[$key] = $value;
      }
    }
    return $temp;
  }

  /**
   * Returns the Julian date of the Windows Excel epoch (1 Jan 1900).
   *
      * @return integer  Julian date
   */
  function _GetExcelEpoch() {
    return GregorianToJD(1,1,1900); // Windows Excel epoch
  }

  /**
   * Initializes the default formats that can be used. After changing
   * the default properties this method has to be called to initialize 
   * the formatting arrays.
   */
  function initFormats() {
    // initialize default formats:
    $text = $this->_getFormatArray();
    $text['textwrap'] = 1;
    $text['numformat'] = '@';
    $this->formats[TEXT_FORMAT] =& $this->workbook->addformat($text);

    $num = $this->_getFormatArray();
    $num['align'] = 'right';
    $this->formats[NUM_FORMAT] =& $this->workbook->addformat($num);

    $num['numformat'] = '[$EUR-413] #,##0.00;[$EUR-413] #,##0.00-';
    $this->formats[MONEY_FORMAT] =& $this->workbook->addformat($num);

    $num['numformat'] = 'dd-mm-yyyy';
    $this->formats[DATE_FORMAT] =& $this->workbook->addformat($num);

    $num['numformat'] = 'hh:mm:ss';
    $this->formats[TIME_FORMAT] =& $this->workbook->addformat($num);

    $num['numformat'] = 'dd-mm-yyyy hh:mm:ss';
    $this->formats[DATETIME_FORMAT] =& $this->workbook->addformat($num);
  }

  /**
   * Creates a worksheet in the Excel file, sets its encoding to UTF-8
   * and returns a reference to the worksheet.
   *
   * @param  string  $name  Name of the worksheet.
     * @return object         Worksheet object.
   */
  function &AddWorksheet($name = NULL) {
    $this->worksheets[] =& $this->workbook->addWorksheet($name);
    $this->worksheets[count($this->worksheets) - 1]->setInputEncoding('UTF-8');
    return $this->worksheets[count($this->worksheets) - 1];
  }

  /**
   * Adds a formatting array to the Excel workbook and returns the index
   * of the array.
   *
   * @param  array  $params  Array with parameters to define formatting.
   *                         Keys refer to the style properties.
     * @return integer         Index of the formatting array.
   */
  function AddFormat($params) {
    $this->formats[] =& $this->workbook->addformat($this->_getFormatArray($params));
    return (count($this->formats) - 1);
  }

  /**
   * Adds a color to the color palette of the workbook.
   *
   * @param  integer $index  Index on the color palette. Existing colors
   *                         will automatically be overridden.
   * @param  mixed   $color  Can be an array of Red, Green and Blue values
   *                         or a hexadecimal representation of the color.
   * @return integer         The palette index for the custom color.
   */
  function setColor($index, $color) {
    if(!is_array($color)) {
      $temp = str_split($color, 2);
      $color[] = hexdec($temp[0]);
      $color[] = hexdec($temp[1]);
      $color[] = hexdec($temp[2]);
    }
    return $this->workbook->setCustomColor($index, $color[0], $color[1], $color[2]);
  }

  /**
   * Converts a MySQL Datetime field value to Excel datetime values.
   *
   * @param string  $datetime  MySQL datetime (dd-mm-yyyy hh:mm:ss)
   * @param float              Excel datetime value.
   */
  function MysqlDatetimeToExcel($datetime) {
    $tmp = explode(" ", $datetime);
    $date = explode("-", $tmp[0]);
    if(isset($tmp[1])) $time = explode(":", $tmp[1]);
    $date1 = GregorianToJD($date[1],$date[2],$date[0]);
    $epoch = $this->_GetExcelEpoch();
    $frac = (($time[0] * 60 * 60) + ($time[1] * 60) + $time[2])/(24*60*60);
    
    return ($date1 - $epoch + 2 + $frac);
  }

  /**
   * Converts a UNIX timestamp value to Excel datetime values.
   *
   * @param int  $timestamp  UNIX timestamp
   * @param float            Excel datetime value.
   */
  function TimestampToExcel($timestamp) {
    return $this->MysqlDatetimeToExcel(date("d-m-Y H:i:s", $timestamp));
  }

  /**
   * Writes a $token (string, number, array, link, formula etc.) to the 
   * specified row and column on the specified worksheet.
   *
   * @param  object   $worksheet  Reference to the worksheet
   * @param  integer  $row        Row number (starting at zero; A1 is 0,0)
   * @param  integer  $col        Column number (starting at zero)
   * @param  mixed    $token      Data to write to the worksheet
   * @param  integer  $format     Index of the formatting array to use
   * @return boolean              False when an error occurs, otherwise True.
   */
  function write(&$worksheet, $row, $col, $token, $format = 0) {
    return $worksheet->write($row, $col, $token, $this->formats[$format]);
  }
  
  /**
   * Sends the temporary Excel file as a string to the render engine
   * and clears all objects.
   */
  function OutputFile() {
    $this->workbook->Close();
    echo file_get_contents($this->workbook->filename, "rb");
  }

}
?>

Layout

You have to create a layout file (excel.thtml) that supports the output of non-HTML files.

View Template:

Download code
<?php
(empty($type)) ? $type = 'applications' : $type = $type;
header("Content-type: application/vnd.ms-excel");
header("Content-Disposition: attachment; filename=slf2007-".$type.".xls");
header("Pragma: no-cache");
header("Expires: 0");
?>
<?php echo $content_for_layout ?>


Application logic

Controller action

In your controller you have to retreive your model data and set it in a variable (e.g. $data), for use in your view. Then you should render the view with the layout 'excel'. Don't forget to list your helper in the $helpers array of your controller.

Controller Class:

Download code <?php 
...
var $helpers = array('Html', 'Form', 'Time', 'Excel');
...
$data = array();
$data['sheet1'] = $this->Model->findAll(NULL, NULL, 'id ASC', NULL, 1, 2);
...    
$this->set('data', $data);
$this->render('action', 'excel');
?>

View

Finally in the view you can use your helper and format your data. You can always use straight library calls by using $excel->worksheet->... or $excel->workbook->...

View Template:

Download code
<?php 

/* Define fieldnames: */
$fieldnames= array('fieldname1', 'fieldname2', etc.);

/* Set default font styles: */
$excel->font = 'Tahoma';
$excel->size = 8;
$excel->initFormats(); // initialize default formats

/* Add style for heading: */
$heading_format = $excel->AddFormat(array('bold' => 1, 'align' => 'center'));

/* Change TIME_FORMAT: */
$excel->formats[TIME_FORMAT]->setNumFormat('hh:mm'); // direct library call

/* Create Excel sheets: */
$sheet1 =& $excel->AddWorksheet('Sheet Name');

/* Define layout of worksheet for applications: */
$sheet1->setColumn(0, 0, 5);
$sheet1->setColumn(7, 10, 8);
$sheet1->setColumn(0, 28, 18);
$sheet1->freezePanes(array(1, 1)); // Freeze sheet at 1st row and 1st column

/* Write headings: */
$excel->write($sheet1, 0, 0, $fieldnames, $heading_format);

/* Write data for applications: */
foreach($data['sheet1'] as $key => $value) {
  $i = 0;
  foreach($data['sheet1'][$key]['Model'] as $fieldname => $fieldvalue) {
    if($fieldname =='birthdate') {
      $excel->write($sheet1, $key+1, $i, $excel->MysqlDatetimeToExcel($fieldvalue), DATE_FORMAT);
    }
    elseif($fieldname == 'created') {
      $excel->write($sheet1, $key+1, $i, $excel->MysqlDatetimeToExcel($fieldvalue), DATETIME_FORMAT);
    }
    elseif($fieldname == 'finances' || $fieldname == 'expenses'){
      $excel->write($sheet1, $key+1, $i, $fieldvalue, MONEY_FORMAT);
    }
    else {
      $excel->write($sheet1, $key+1, $i, $fieldvalue);
    }
    $i++;
  }
}

/* Output temporary file to the browser: */
$excel->OutputFile();

?>

That should result in a nice Excel file. Of course you can use many more options (like including graphics and hyperlinks, adding borders, colors, etc.). For more information you can check the documentation of PEAR's Spreadsheet_Excel_Writer class (http://pear.php.net/package/Spreadsheet_Excel_Writer/docs).

Warning!

On *NIX systems you should take care that you don't leave any spaces after the closing PHP-tags. This will result in the "headers already sent" error.