用PHP编写简单的RSS阅读器

代码如下：

<?php /** * Simple reader for RSS and Atom feeds. * Requires: SimpleXML, fopen_wrappers * Limitations: Not content encoding support. * * Usage: * $feed = new Feed('http://www.example.com/feed.rss'); * * //Get items with next() or current() * echo $feed->next()->title; // "Blog post 1" * echo $feed->next()->title; // "Blog post 1" * echo $feed->next()->title; // "Blog post 2" * echo $feed->current()->title; // "Blog post 2" * * //Feed data returned * echo $feed->current()->title; // "Blog post 2" * echo $feed->current()->date; // int(1265569159) * echo $feed->current()->description; // "Lorem ipsum dolar..." * echo $feed->current()->link; // "http://www.example.com/blog/2" * echo $feed->current()->image; // "http://www.example.com/blog/images/2.jpg" * * //Get multiple items in single call * foreach ($feed->find(3) as $item) { * echo $item->title; // "Blog post 3" "Blog post 4" "Blog post 5" * } * * //Reset internal counter * echo $feed->reset(); * echo $feed->next()->title; // "Blog post 1" * * //Get random items, without repeating * echo $feed->random()->title; // "Blog post 4" * echo $feed->random()->title; // "Blog post 3" * * //Total number of items * echo $feed->count(); // int(10) */ class Feed { private $url; private $reader; private $current; private $remaining; public $cacheTime = 3600; /** * Create Atom reader object. * * @param string $url */ public function __construct($url) { $this->url = $url; $this->reset(); } /** * Reset current item to first RSS item. */ public function reset() { $this->current = -1; $this->remaining = null; } /** * Get the next item in the feed. * * @return stdClass Object representing the item. Will return null when the list is exhausted. */ public function next() { if ($this->current < $this->count()) { $this->current++; $next = $this->getReader()->item($this->current); return $next; } } /** * Get the current item in the feed. * * @return stdClass Object representing the item. Will return null when the list is exhausted. */ public function current() { return $this->getReader()->item(max(0, $this->current)); } /** * Get random item from the feed. Will not return an item more than once. * * @return stdClass Object representing the item. Will return null when the list is exhausted. */ public function random() { if ($this->remaining === null) { $this->remaining = array(); for ($i = 0; $i < $this->count(); $i++) { $this->remaining[] = $i; } } if (count($this->remaining)) { $picked = array_rand($this->remaining); $index = $this->remaining[$picked]; unset($this->remaining[$picked]); return $this->getReader()->item($index); } } /** * Get X items from feed. Will advance pointer. * * @param int $count * @return array of stdClass */ public function find($count) { $items = array(); while ($item = $this->next()) { $items[] = $item; if (count($items) >= $count) { break; } } return $items; } /** * Get the number of items in the feed. * * @return int */ public function count() { return $this->getReader()->count(); } /** * Get FeedReader object for the feed. * * @return FeedReader */ private function getReader() { if (!$this->reader) { $xml = $this->getXML(); if (RSSReader::canRead($xml)) { $this->reader = new RSSReader($xml); } else if (AtomReader::canRead($xml)) { $this->reader = new AtomReader($xml); } else { $this->reader = new NullReader($xml); } } return $this->reader; } /** * Get XML element for the feed. * * @return SimpleXMLElement */ private function getXML() { if ($xml = $this->getCacheXML()) { return $xml; } else if ($xml = $this->getURLXML()) { return $xml; } else { return new SimpleXMLElement(""); } } /** * Get XML element for the feed from cache. * * @return SimpleXMLElement or null if cache doesn't exist. */ private function getCacheXML() { //Store URL data in local cache. $cacheFilename = $this->getCacheFilename(); if (file_exists($cacheFilename) && (time() - filemtime($cacheFilename)) < $this->cacheTime) { if ($data = file_get_contents($cacheFilename)) { return new SimpleXMLElement($data); } } } /** * Get XML element from the feed from the live URL. * Will cache XML data to disk. * * @return SimpleXMLElement or null if URL is unreachable. */ private function getURLXML() { if ($data = @file_get_contents($this->url)) { try { $xml = new SimpleXMLElement($data); file_put_contents($this->getCacheFilename(), $data); return $xml; } catch (Exception $e) { return null; } } } /** * Name of the cache file for current URL. * * @return string */ private function getCacheFilename() { return sys_get_temp_dir() . '/' . md5($this->url) . '.feed.cache'; } } /** * Interface for reading items from feed. */ interface FeedReader { /** * Create reader from SimpleXMLElement. * * @param SimpleXMLElement $root */ public function __construct(SimpleXMLElement $root); /** * Get single node. * * @return array or null. */ public function item($index); /** * Get number of items. * * @return int. */ public function count(); /** * Can this reader understand the XML file? * * @param SimpleXMLElement $root * @return bool */ public static function canRead(SimpleXMLElement $root); } /** * Concrete implementation of FeedReader that will never return an item. */ class NullReader implements FeedReader { public function __construct(SimpleXMLElement $root) { //Nothing } public function count() { return null; } public function item($index) { return null; } public static function canRead(SimpleXMLElement $root) { return true; } } /** * Concrete implementation of FeedReader that will read an Atom feed. */ class AtomReader implements FeedReader { private $root; public function __construct(SimpleXMLElement $root) { $this->root = $root; } public function count() { return count($this->root->entry); } public function item($index) { $node = $this->root->entry[$index]; if (!$node) { return null; } $item = array( 'title' => (string)$node->title, 'description' => (string)$node->description, 'image' => null, 'link' => null, 'date' => strtotime($node->published), ); //Iterate through link nodes getting content URL and images. foreach ($node->link as $link) { if (strpos($link['type'], 'text') === 0 || $item['link'] === null) { $item['link'] = (string)$link['href']; } if (strpos($link['type'], 'image') === 0) { $item['image'] = (string)$link['href']; } } return (object)$item; } public static function canRead(SimpleXMLElement $root) { //Check for Atom namespace. return in_array('http://www.w3.org/2005/Atom', $root->getNamespaces()); } } /** * Concrete implementation of FeedReader that will read an RSS feed. */ class RSSReader implements FeedReader { private $root; public function __construct(SimpleXMLElement $root) { $this->root = $root; } public function count() { return count($this->root->channel->item); } public function item($index) { $node = $this->root->channel->item[$index]; if (!$node) { return null; } return (object)array( 'title' => (string)$node->title, 'description' => (string)$node->description, 'url' => (string)$node->link, 'image' => null, 'date' => strtotime($node->pubDate), ); } public static function canRead(SimpleXMLElement $root) { //RSS feeds name their root node 'rss'. return $root->getName() == 'rss'; } }

 

 

21CTO译，原址：http://www.21cto.com/webdeveloper/php/2010/1218/4403.html

英文原文：http://joshduck.com/blog/2010/02/08/simple-atom-rss-reader-for-php/