Writing CSV Files Using Drupal

I'm leaving this one here, mostly as a note for myself. I've found too often that samples on the web, and indeed in existing code I inherit are chalked full of 'doing it the hard way' and memory leaks. This is the simplest and cleanest method for handling streaming large amounts of data out to a csv.

function _write_csv(){
  $path = 'public://{directory}/{subdirectory}/';
  $filename = '{something}-' . REQUEST_TIME . '.csv';
  // Ensure the directory
  if( !file_prepare_directory($path, FILE_CREATE_DIRECTORY) ){
    drupal_set_message( t('Unable to create directory in file system. Check permissions and try again.'), 'error' );
    return;
  }
  // Ensure the file
  $file = file_save_data('', $path . $filename);
  if( !$file ){
    drupal_set_message( t('Unable to write to file system. Check permissions and try again.'), 'error' );
    return;
  }
  // Stream data - This is a simplified example. Better to do it in a batch if you have a high volume of data
  $fh = fopen($file->uri, 'w');
  if( !$fh ){
    drupal_set_message( t('Unable open file for writing. Check permissions and try again.'), 'error' );
    return;
  }
  fputcsv($fh, array(
    'Column 1',
    'Column 2',
  ));
  for($i = 0; $i < 3; ++$i){
    fputcsv($fh, array(
      'Column 1 - ' . $i,
      'Column 2 - ' . $i,
    ));
  }
  fclose($fh);
  // Notify the filesystem of the size change
  $file->filesize = filesize($file->uri);
  file_save($file);
  // Tell the user where we stuck it
  drupal_set_message( t('Export complete. <a href="!url">!filename</a>.', array(
    '!url' => file_create_url($file->uri),
    '!filename' => $filename,
  )));
}
function _write_csv(){
  $path = 'public://{directory}/{subdirectory}/';
  $filename = '{something}-' . REQUEST_TIME . '.csv';
  // Ensure the directory
  if( !file_prepare_directory($path, FILE_CREATE_DIRECTORY) ){
    drupal_set_message( t('Unable to create directory in file system. Check permissions and try again.'), 'error' );
    return;
  }
  // Ensure the file
  $file = file_save_data('', $path . $filename);
  if( !$file ){
    drupal_set_message( t('Unable to write to file system. Check permissions and try again.'), 'error' );
    return;
  }
  // Stream data - This is a simplified example. Better to do it in a batch if you have a high volume of data
  $fh = fopen($file->uri, 'w');
  if( !$fh ){
    drupal_set_message( t('Unable open file for writing. Check permissions and try again.'), 'error' );
    return;
  }
  fputcsv($fh, array(
    'Column 1',
    'Column 2',
  ));
  for($i = 0; $i < 3; ++$i){
    fputcsv($fh, array(
      'Column 1 - ' . $i,
      'Column 2 - ' . $i,
    ));
  }
  fclose($fh);
  // Notify the filesystem of the size change
  $file->filesize = filesize($file->uri);
  file_save($file);
  // Tell the user where we stuck it
  drupal_set_message( t('Export complete. <a href="!url">!filename</a>.', array(
    '!url' => file_create_url($file->uri),
    '!filename' => $filename,
  )));
}