PHP Link Scraper Class

Need to suck URL-s (A tags) from a page but don't know where to start ? Steal this!

It also implements the ArrayAccess and Iterator interfaces so you can use it as an array to access the links and also in a foreach loop as well in the usual manner. I have made the array setter functions die() as that's what I wanted but it you be a simple (exercise for the reader!) matter to change that should you want to.

 /*!
   * @file PageSucker.class.php
   * @author Sean Charles sean at objitsu dot com
   * @date   28th March 2011
   *
   * PageSucker - Extract all A links from a page and optionally remove all of
   * those that are not 'on-site'. This is achieved by passing in the full URL
   * to the constructor i.e. "http://foo.bar.com" which enables a simplistic
   * check to know what's local and what isn't.
   *
   * @licence Do what you will with it but a link back would be nice and also
   * knowing what you used it for is also of interest! Thanks. :)
   *
   * This class implements the following interfaces: Iterator, ArrayAccess
   * which means you can treat is just like an array m aking it very easy to
   * process the links it finds at any given location.
   *
   * I have made it IMMUTABLE: If you try to change the contents of it after
   * it has been loaded it will die. You can change that if you want.
   *
   * Typical Usage:
   *
   * $links = new PageSucker("http://google.com");
   * echo $links[0];
   * $links[0] = "something"; // will die() as you cannot change its contents.
   *
   * foreach ($links as $l) {
   *   echo $l . '<br />';
   * }
   * 
   */
class PageSucker implements Iterator, ArrayAccess, Countable
{
  private $url;
  private $parsed_url;
  private $links;
  private $index;
  private $maxlen;

  /*!
   * @param $url is the URL to scrape. MUST start with http: in order for the
   * offsite link removal to function correctly.
   *
   * @param $offsite = TRUE to keep all links, otherwise the list will be
   * purged of all offsite links meaning this class can be used to build a
   * site-map.
   */
  public function __construct($url, $offsite = TRUE, $rejectRSS = TRUE)
  {
    $this->links = array();
    //!
    //! Clean and rebuild the URL we've been given.
    //!
    $this->parsed_url  = parse_url(trim($url));
    $this->parsed_url += 
      array('scheme' => 'http',
            'port'   => 80,
            'path'   => '/');

    //! Rebuild a cleaned URL for internal use ...
    $this->url 
      = $this->parsed_url['scheme'] . '://'
      . $this->parsed_url['host']   . ':'
      . $this->parsed_url['port']
      . $this->parsed_url['path'];
    $this->len = strlen($this->url);
    echo "SCAN URL: {$this->url}\n";

    $html = file_get_contents($this->url);
    $matches = array();

    preg_match_all(
      "/a[\s]+[^>]*?href[\s]?=[\s\"\']+(.*?)[\"\']+.*?>([^<]+|.*?)?<\/a>/",
      $html,
      &$matches);
    
    $links = array_unique($matches[1]);

    if (!$offsite) {
      $links = array_filter($links, array($this, '_purgeOffsite'));
    }
    if ($rejectRSS) {
      $links = array_filter($links, array($this, '_purgeRSS'));
    }

    $links        = array_map(array($this, '_normalise'), $links);
    $this->links  = array_values($links);
    $this->maxlen = count($this->links);
    $this->index  = 0;
  }

  /*!
   * Make all links absolute.
   */
  private function _normalise($link)
  {
    $link  = trim($link);
    $parts = explode('?', $link);
    $link  = $parts[0];
    if ($link[0] == '/') {
      $link = $this->url . substr($link,1);
    }
    return $link;
  }

  /*!
   * Filters out links that do not start with '/' and who's prefix is offsite.
   */
  private function _purgeOffsite($link) {
    if ($link[0] != '/') {
      return 0 == strncasecmp(
        $this->url,
        $link, $this->len);
    }
    return TRUE;
  }

  /*!
   * Filters out RSS feeds.
   */
  private function _purgeRSS($link) {
    return ".xml" !== strtolower(substr($link,-4));
  }

  // --------------------------------------------------------------------
  // Iterator
  // --------------------------------------------------------------------
  public function current() {
    return $this->links[$this->index];
  }
  public function key() {
    return $this->index;
  }
  public function next() {
    $this->index++;
  }
  public function valid() {
    return $this->index < $this->maxlen;
  }
  public function rewind() {
    $this->index = 0;
  }

  // --------------------------------------------------------------------
  // ArrayAccess
  // --------------------------------------------------------------------
  public function offsetExists($offset) {
    return isset($this->links[$offset]);
  }
  public function offsetGet($offset) {
    return isset($this->links[$offset])
      ? $this->links[$offset]
      : NULL;
  }
  public function offsetSet($offset, $value) {
    die("I don't want to be mutable"); }
  public function offsetUnset($offset) {
    die("I don't want to be mutable"); }
  // --------------------------------------------------------------------
  // Countable
  // --------------------------------------------------------------------
  public function count() {
    return count($this->links);
  }
}