array2XML_example.php

<?php  
  // Structered array for convertion into XML.
  $data_array = array(
    array(
      '#xml_tag' => 'a',
      '#xml_value' => '',
      '#tag_attributes' => array(
        array(
          'name' => 'a_attr_name',
          'value' => 'a_attr_value',
        ),
      ),
      '#subnode' => array(
        array(
          '#xml_tag' => 'aa',
          '#xml_value' => 'aa_value',
          '#tag_attributes' => array(
            array(
              'name' => 'aa_attr_name',
              'value' => 'aa_attr_value',
            ),
          ),
          '#subnode' => FALSE,
        ),
      ),
    ),
    array(
      '#xml_tag' => 'b',
      '#xml_value' => 'b_value',
      '#tag_attributes' => FALSE,
      '#subnode' => FALSE,
    ),
    array(
      '#xml_tag' => 'c',
      '#xml_value' => 'c_value',
      '#tag_attributes' => array(
        array(
          'name' => 'c_attr_name',
          'value' => 'c_attr_value',
        ),
        array(
          'name' => 'c_attr_name_1',
          'value' => 'c_attr_value_1',
        ),
      ),
      '#subnode' => array(
        array(
          '#xml_tag' => 'ca',  
          '#xml_value' => 'ca_value',
          '#tag_attributes' => FALSE,
          '#subnode' => array(
            array(
              '#xml_tag' => 'caa',
              '#xml_value' => 'caa_value',
              '#tag_attributes' => array(
                array(
                  'name' => 'caa_attr_name',
                  'value' => 'caa_attr_value',
                ),
              ),
              '#subnode' => FALSE,
            ),
          ),
        ),
      ),
    ),
  );

  // creating object of SimpleXMLElement
  $xml_object = new SimpleXMLElement('<?xml version="1.0" encoding="UTF-8" ?><nfeProc versao="2.00" xmlns="http://www.portalfiscal.inf.br/nfe"></nfeProc>');

  // function call to convert array to xml
  // See https://gist.github.com/drupalista-br/9230202
  array_to_xml($data_array, $xml_object);

  // saving generated xml file
  $xml_object->asXML('/tmp/test.xml');