Something

						foreach($xml->data->item as $key => $value)
						{
							if(isset($value->foobar))
							{
								foreach($value->number as $eKey => $eValue)
								{
									$html_data[$eValue->a][$eValue->b][] = $eValue->a . $eValue->b . $eValue->c;
									$html_data[$eValue->a][$eValue->b][] = '<input type="checkbox" name="abc[]" id="abc_id" />';
								}
							}
						}