Analyse D'énormes fichiers XML en PHP

il s'agit d'une question très similaire à meilleure façon de traiter grand XML en PHP , mais avec une très bonne réponse spécifique rétrogradé abordant le problème spécifique de DMOZ parsing catalogue. Cependant, comme il s'agit d'un bon succès de Google pour les grands XMLs en général, je vais reposer ma réponse de l'autre question aussi bien:

Mon prendre sur elle:

https://github.com/prewk/XmlStreamer

une classe simple qui extraira tous les enfants vers L'élément racine XML en streamant le fichier. Testé sur un fichier XML de 108 Mo à partir de pubmed.com.

class SimpleXmlStreamer extends XmlStreamer {
    public function processNode($xmlString, $elementName, $nodeIndex) {
        $xml = simplexml_load_string($xmlString);

        // Do something with your SimpleXML object

        return true;
    }
}

$streamer = new SimpleXmlStreamer("myLargeXmlFile.xml");
$streamer->parse();

j'ai récemment dû analyser des documents XML assez volumineux, et j'avais besoin d'une méthode pour lire un élément à la fois.

si vous avez le fichier complex-test.xml suivant:

<?xml version="1.0" encoding="UTF-8"?>
<Complex>
  <Object>
    <Title>Title 1</Title>
    <Name>It's name goes here</Name>
    <ObjectData>
      <Info1></Info1>
      <Info2></Info2>
      <Info3></Info3>
      <Info4></Info4>
    </ObjectData>
    <Date></Date>
  </Object>
  <Object></Object>
  <Object>
    <AnotherObject></AnotherObject>
    <Data></Data>
  </Object>
  <Object></Object>
  <Object></Object>
</Complex>

et a voulu rendre le <Object/> s

PHP:

require_once('class.chunk.php');

$file = new Chunk('complex-test.xml', array('element' => 'Object'));

while ($xml = $file->read()) {
  $obj = simplexml_load_string($xml);
  // do some parsing, insert to DB whatever
}

###########
Class File
###########

<?php
/**
 * Chunk
 * 
 * Reads a large file in as chunks for easier parsing.
 * 
 * The chunks returned are whole <$this->options['element']/>s found within file.
 * 
 * Each call to read() returns the whole element including start and end tags.
 * 
 * Tested with a 1.8MB file, extracted 500 elements in 0.11s
 * (with no work done, just extracting the elements)
 * 
 * Usage:
 * <code>
 *   // initialize the object
 *   $file = new Chunk('chunk-test.xml', array('element' => 'Chunk'));
 *   
 *   // loop through the file until all lines are read
 *   while ($xml = $file->read()) {
 *     // do whatever you want with the string
 *     $o = simplexml_load_string($xml);
 *   }
 * </code>
 * 
 * @package default
 * @author Dom Hastings
 */
class Chunk {
  /**
   * options
   *
   * @var array Contains all major options
   * @access public
   */
  public $options = array(
    'path' => './',       // string The path to check for $file in
    'element' => '',      // string The XML element to return
    'chunkSize' => 512    // integer The amount of bytes to retrieve in each chunk
  );

  /**
   * file
   *
   * @var string The filename being read
   * @access public
   */
  public $file = '';
  /**
   * pointer
   *
   * @var integer The current position the file is being read from
   * @access public
   */
  public $pointer = 0;

  /**
   * handle
   *
   * @var resource The fopen() resource
   * @access private
   */
  private $handle = null;
  /**
   * reading
   *
   * @var boolean Whether the script is currently reading the file
   * @access private
   */
  private $reading = false;
  /**
   * readBuffer
   * 
   * @var string Used to make sure start tags aren't missed
   * @access private
   */
  private $readBuffer = '';

  /**
   * __construct
   * 
   * Builds the Chunk object
   *
   * @param string $file The filename to work with
   * @param array $options The options with which to parse the file
   * @author Dom Hastings
   * @access public
   */
  public function __construct($file, $options = array()) {
    // merge the options together
    $this->options = array_merge($this->options, (is_array($options) ? $options : array()));

    // check that the path ends with a /
    if (substr($this->options['path'], -1) != '/') {
      $this->options['path'] .= '/';
    }

    // normalize the filename
    $file = basename($file);

    // make sure chunkSize is an int
    $this->options['chunkSize'] = intval($this->options['chunkSize']);

    // check it's valid
    if ($this->options['chunkSize'] < 64) {
      $this->options['chunkSize'] = 512;
    }

    // set the filename
    $this->file = realpath($this->options['path'].$file);

    // check the file exists
    if (!file_exists($this->file)) {
      throw new Exception('Cannot load file: '.$this->file);
    }

    // open the file
    $this->handle = fopen($this->file, 'r');

    // check the file opened successfully
    if (!$this->handle) {
      throw new Exception('Error opening file for reading');
    }
  }

  /**
   * __destruct
   * 
   * Cleans up
   *
   * @return void
   * @author Dom Hastings
   * @access public
   */
  public function __destruct() {
    // close the file resource
    fclose($this->handle);
  }

  /**
   * read
   * 
   * Reads the first available occurence of the XML element $this->options['element']
   *
   * @return string The XML string from $this->file
   * @author Dom Hastings
   * @access public
   */
  public function read() {
    // check we have an element specified
    if (!empty($this->options['element'])) {
      // trim it
      $element = trim($this->options['element']);

    } else {
      $element = '';
    }

    // initialize the buffer
    $buffer = false;

    // if the element is empty
    if (empty($element)) {
      // let the script know we're reading
      $this->reading = true;

      // read in the whole doc, cos we don't know what's wanted
      while ($this->reading) {
        $buffer .= fread($this->handle, $this->options['chunkSize']);

        $this->reading = (!feof($this->handle));
      }

      // return it all
      return $buffer;

    // we must be looking for a specific element
    } else {
      // set up the strings to find
      $open = '<'.$element.'>';
      $close = '</'.$element.'>';

      // let the script know we're reading
      $this->reading = true;

      // reset the global buffer
      $this->readBuffer = '';

      // this is used to ensure all data is read, and to make sure we don't send the start data again by mistake
      $store = false;

      // seek to the position we need in the file
      fseek($this->handle, $this->pointer);

      // start reading
      while ($this->reading && !feof($this->handle)) {
        // store the chunk in a temporary variable
        $tmp = fread($this->handle, $this->options['chunkSize']);

        // update the global buffer
        $this->readBuffer .= $tmp;

        // check for the open string
        $checkOpen = strpos($tmp, $open);

        // if it wasn't in the new buffer
        if (!$checkOpen && !($store)) {
          // check the full buffer (in case it was only half in this buffer)
          $checkOpen = strpos($this->readBuffer, $open);

          // if it was in there
          if ($checkOpen) {
            // set it to the remainder
            $checkOpen = $checkOpen % $this->options['chunkSize'];
          }
        }

        // check for the close string
        $checkClose = strpos($tmp, $close);

        // if it wasn't in the new buffer
        if (!$checkClose && ($store)) {
          // check the full buffer (in case it was only half in this buffer)
          $checkClose = strpos($this->readBuffer, $close);

          // if it was in there
          if ($checkClose) {
            // set it to the remainder plus the length of the close string itself
            $checkClose = ($checkClose + strlen($close)) % $this->options['chunkSize'];
          }

        // if it was
        } elseif ($checkClose) {
          // add the length of the close string itself
          $checkClose += strlen($close);
        }

        // if we've found the opening string and we're not already reading another element
        if ($checkOpen !== false && !($store)) {
          // if we're found the end element too
          if ($checkClose !== false) {
            // append the string only between the start and end element
            $buffer .= substr($tmp, $checkOpen, ($checkClose - $checkOpen));

            // update the pointer
            $this->pointer += $checkClose;

            // let the script know we're done
            $this->reading = false;

          } else {
            // append the data we know to be part of this element
            $buffer .= substr($tmp, $checkOpen);

            // update the pointer
            $this->pointer += $this->options['chunkSize'];

            // let the script know we're gonna be storing all the data until we find the close element
            $store = true;
          }

        // if we've found the closing element
        } elseif ($checkClose !== false) {
          // update the buffer with the data upto and including the close tag
          $buffer .= substr($tmp, 0, $checkClose);

          // update the pointer
          $this->pointer += $checkClose;

          // let the script know we're done
          $this->reading = false;

        // if we've found the closing element, but half in the previous chunk
        } elseif ($store) {
          // update the buffer
          $buffer .= $tmp;

          // and the pointer
          $this->pointer += $this->options['chunkSize'];
        }
      }
    }

    // return the element (or the whole file if we're not looking for elements)
    return $buffer;
  }
}

je suggère d'utiliser un analyseur SAX plutôt qu'un analyseur DOM.

Info sur l'utilisation de SAX en PHP: http://www.brainbell.com/tutorials/php/Parsing_XML_With_SAX.htm

ce n'est pas une bonne solution, mais juste pour jeter une autre option là-bas:

vous pouvez casser beaucoup de gros fichiers XML en morceaux, surtout ceux qui ne sont que des listes d'éléments similaires (comme je soupçonne le fichier avec lequel vous travaillez).

par exemple, si votre doc ressemble à:

<dmoz>
  <listing>....</listing>
  <listing>....</listing>
  <listing>....</listing>
  <listing>....</listing>
  <listing>....</listing>
  <listing>....</listing>
  ...
</dmoz>

vous pouvez le lire dans un meg ou deux à la fois, envelopper artificiellement les quelques étiquettes complètes <listing> vous avez chargé dans un étiquette de niveau de racine, puis les charger via simplexml / domxml (j'ai utilisé domxml, en adoptant cette approche).

franchement, je préfère cette approche si vous utilisez PHP < 5.1.2. Avec 5.1.2 et plus, XMLReader est disponible, ce qui est probablement la meilleure option, mais avant cela, vous êtes coincé avec soit la stratégie de chunking ci-dessus, ou l'ancienne lib SAX/expat. Et je ne sais pas pour le reste d'entre vous, mais je déteste écrire/maintenir des parsers SAX/expat.

Note, cependant, cette approche N'est pas vraiment pratique lorsque votre document ne comprend pas de nombreux éléments identiques de base (par exemple, il fonctionne très bien pour toute sorte de liste de fichiers, ou URLs, etc). mais ne serait pas logique pour l'analyse d'un grand document HTML)