<?php

/**
 * Array2XML: A class to convert array in PHP to XML
 * It also takes into account attributes names unlike SimpleXML in PHP
 * It returns the XML in form of DOMDocument class for further manipulation.
 * It throws exception if the tag name or attribute name has illegal chars.
 *
 * Author : Lalit Patel
 * Website: http://www.lalit.org/lab/convert-php-array-to-xml-with-attributes
 * License: Apache License 2.0
 *          http://www.apache.org/licenses/LICENSE-2.0
 * Version: 0.1 (10 July 2011)
 * Version: 0.2 (16 August 2011)
 *          - replaced htmlentities() with htmlspecialchars() (Thanks to Liel Dulev)
 *          - fixed a edge case where root node has a false/null/0 value. (Thanks to Liel Dulev)
 * Version: 0.3 (22 August 2011)
 *          - fixed tag sanitize regex which didn't allow tagnames with single character.
 * Version: 0.4 (18 September 2011)
 *          - Added support for CDATA section using @cdata instead of @value.
 * Version: 0.5 (07 December 2011)
 *          - Changed logic to check numeric array indices not starting from 0.
 * Version: 0.6 (04 March 2012)
 *          - Code now doesn't @cdata to be placed in an empty array
 * Version: 0.7 (24 March 2012)
 *          - Reverted to version 0.5
 * Version: 0.8 (02 May 2012)
 *          - Removed htmlspecialchars() before adding to text node or attributes.
 *
 * - Mar 8, 2017 - Formatting
 *
 * Usage:
 *       $xml = Array2XML::createXML('root_node_name', $php_array);
 *       echo $xml->saveXML();
 */
class Array2XML {

  private static $xml = null;
  private static $encoding = 'UTF-8';
  public static $all_caps = false;

  /**
   * Initialize the root XML node [optional]
   * @param $version
   * @param $encoding
   * @param $format_output
   */
  public static function init($version = '1.0', $encoding = 'UTF-8', $format_output = true) {
    self::$xml = new DomDocument($version, $encoding);
    self::$xml->formatOutput = $format_output;
    self::$encoding = $encoding;
  }

  /**
   * Convert an Array to XML
   * @param string $node_name - name of the root node to be converted
   * @param array $arr - array to be converted
   * @return DomDocument
   */
  public static function &createXML($node_name, $arr = array()) {
    $xml = self::getXMLRoot();
    $xml->appendChild(self::convert($node_name, $arr));

    self::$xml = null;    // clear the xml node in the class for 2nd time use.
    return $xml;
  }

  /**
   * Convert an Array to XML
   * @param string $node_name - name of the root node to be converted
   * @param array $arr - array to be converted
   * @return DOMNode
   */
  private static function &convert($node_name, $arr = array()) {

    //print_arr($node_name);
    $xml = self::getXMLRoot();
    $node = $xml->createElement($node_name);

    if (is_array($arr)) {
      // get the attributes first.;
      if (isset($arr['@attributes'])) {
        foreach ($arr['@attributes'] as $key => $value) {
          if (!self::isValidTagName($key)) {
            throw new Exception('[Array2XML] Illegal character in attribute name. attribute: ' . $key . ' in node: ' . $node_name);
          }
          $node->setAttribute($key, self::bool2str($value));
        }
        unset($arr['@attributes']); //remove the key from the array once done.
      }

      // check if it has a value stored in @value, if yes store the value and return
      // else check if its directly stored as string
      if (isset($arr['@value'])) {
        $node->appendChild($xml->createTextNode(self::bool2str($arr['@value'])));
        unset($arr['@value']);    //remove the key from the array once done.
        //return from recursion, as a note with value cannot have child nodes.
        return $node;
      }
      else if (isset($arr['@cdata'])) {
        $node->appendChild($xml->createCDATASection(self::bool2str($arr['@cdata'])));
        unset($arr['@cdata']);    //remove the key from the array once done.
        //return from recursion, as a note with cdata cannot have child nodes.
        return $node;
      }
    }

    //create subnodes using recursion
    if (is_array($arr)) {
      // recurse to get the node for that key
      foreach ($arr as $key => $value) {
        if (!self::isValidTagName($key)) {
          throw new Exception('[Array2XML] Illegal character in tag name. tag: ' . $key . ' in node: ' . $node_name);
        }
        $key = self::$all_caps ? strtoupper($key) : $key;
        if (is_array($value) && is_numeric(key($value))) {
          // MORE THAN ONE NODE OF ITS KIND;
          // if the new array is numeric index, means it is array of nodes of the same kind
          // it should follow the parent key name
          foreach ($value as $k => $v) {
            $node->appendChild(self::convert($key, $v));
          }
        }
        else {
          // ONLY ONE NODE OF ITS KIND
          $node->appendChild(self::convert($key, $value));
        }
        unset($arr[$key]); //remove the key from the array once done.
      }
    }

    // after we are done with all the keys in the array (if it is one)
    // we check if it has any text value, if yes, append it.
    if (!is_array($arr)) {
      $node->appendChild($xml->createTextNode(self::bool2str($arr)));
    }

    return $node;
  }

  /*
   * Get the root XML node, if there isn't one, create it.
   */

  private static function getXMLRoot() {
    if (empty(self::$xml)) {
      self::init();
    }
    return self::$xml;
  }

  /*
   * Get string representation of boolean value
   */

  private static function bool2str($v) {
    //convert boolean to text value.
    $v = $v === true ? 'true' : $v;
    $v = $v === false ? 'false' : $v;
    return $v;
  }

  /*
   * Check if the tag name or attribute name contains illegal characters
   * Ref: http://www.w3.org/TR/xml/#sec-common-syn
   */

  private static function isValidTagName($tag) {
    $pattern = '/^[a-z_]+[a-z0-9\:\-\.\_]*[^:]*$/i';
    return preg_match($pattern, $tag, $matches) && $matches[0] == $tag;
  }

}