Feed parsing
============

Parsing a subscription
----------------------

```php
use PicoFeed\Reader\Reader;
use PicoFeed\PicoFeedException;

try {

    $reader = new Reader;

    // Return a resource
    $resource = $reader->download('http://linuxfr.org/news.atom');

    // Return the right parser instance according to the feed format
    $parser = $reader->getParser(
        $resource->getUrl(),
        $resource->getContent(),
        $resource->getEncoding()
    );

    // Return a Feed object
    $feed = $parser->execute();

    // Print the feed properties with the magic method __toString()
    echo $feed;
}
catch (PicoFeedException $e) {
    // Do Something...
}
```

- The Reader class is the entry point for feed reading
- The method `download()` fetch the remote content and return a resource, an instance of `PicoFeed\Client\Client`
- The method `getParser()` returns a Parser instance according to the feed format Atom, Rss 2.0...
- The parser itself returns a `Feed` object that contains feed and item properties

Output:

```bash
Feed::id = tag:linuxfr.org,2005:/news
Feed::title = LinuxFr.org : les dépêches
Feed::url = http://linuxfr.org/news
Feed::date = 1415138079
Feed::language = en-US
Feed::description =
Feed::logo =
Feed::items = 15 items
----
Item::id = 38d8f48284fb03940cbb3aff9101089b81e44efb1281641bdd7c3e7e4bf3b0cd
Item::title = openSUSE 13.2 : nouvelle version du caméléon disponible !
Item::url = http://linuxfr.org/news/opensuse-13-2-nouvelle-version-du-cameleon-disponible
Item::date = 1415122640
Item::language = en-US
Item::author = Syvolc
Item::enclosure_url =
Item::enclosure_type =
Item::content = 18307 bytes
....
```

Get the list of available subscriptions for a website
-----------------------------------------------------

The example below will returns all available subscriptions for the website:

```php
use PicoFeed\Reader\Reader;

try {

    $reader = new Reader;
    $resource = $reader->download('http://www.cnn.com');

    $feeds = $reader->find(
        $resource->getUrl(),
        $resource->getContent()
    );

    print_r($feeds);
}
catch (PicoFeedException $e) {
    // Do something...
}
```

Output:

```php
Array
(
    [0] => http://rss.cnn.com/rss/cnn_topstories.rss
    [1] => http://rss.cnn.com/rss/cnn_latest.rss
)
```

Feed discovery and parsing
--------------------------

This example will discover automatically the subscription and parse the feed:

```php
try {

    $reader = new Reader;
    $resource = $reader->discover('http://linuxfr.org');

    $parser = $reader->getParser(
        $resource->getUrl(),
        $resource->getContent(),
        $resource->getEncoding()
    );

    $feed = $parser->execute();
    echo $feed;
}
catch (PicoFeedException $e) {
}
```

HTTP caching
------------

PicoFeed supports HTTP caching to avoid unnecessary processing.

1. After the first download, save in your database the values of the Etag and LastModified HTTP headers
2. For the next requests, provide those values to the `download()` method and check if the feed was modified or not

Here an example:

```php
try {

    // Fetch from your database the previous values of the Etag and LastModified headers
    $etag = '...';
    $last_modified = '...';

    $reader = new Reader;

    // Provide those values to the download method
    $resource = $reader->download('http://linuxfr.org/news.atom', $last_modified, $etag);

    // Return true if the remote content has changed
    if ($resource->isModified()) {

        $parser = $reader->getParser(
            $resource->getUrl(),
            $resource->getContent(),
            $resource->getEncoding()
        );

        $feed = $parser->execute();

        // Save your feed in your database
        // ...

        // Store the Etag and the LastModified headers in your database for the next requests
        $etag = $resource->getEtag();
        $last_modified = $resource->getLastModified();

        // ...
    }
    else {

        echo 'Not modified, nothing to do!';
    }
}
catch (PicoFeedException $e) {
    // Do something...
}
```


Feed and item properties
------------------------

```php
// Feed object
$feed->getId();              // Unique feed id
$feed->getTitle();           // Feed title
$feed->getUrl();             // Website url
$feed->getDate();            // Feed last updated date
$feed->getLanguage();        // Feed language
$feed->getDescription();     // Feed description
$feed->getLogo();            // Feed logo (can be a large image, different from icon)
$feed->getItems();           // List of item objects

// Item object
$feed->items[0]->getId();                      // Item unique id (hash)
$feed->items[0]->getTitle();                   // Item title
$feed->items[0]->getUrl();                     // Item url
$feed->items[0]->getDate();                    // Item published date (timestamp)
$feed->items[0]->getLanguage();                // Item language
$feed->items[0]->getAuthor();                  // Item author
$feed->items[0]->getEnclosureUrl();            // Enclosure url
$feed->items[0]->getEnclosureType();           // Enclosure mime-type (audio/mp3, image/png...)
$feed->items[0]->getContent();                 // Item content (filtered or raw)
```

RTL language detection
----------------------

There is an utility method to determine if a language code is Right-To-Left or not:

```php
// Return true if RTL
Parser::isLanguageRTL($item->getLanguage());
```

Known RTL languages are:

- Arabic (ar-**)
- Farsi (fa-**)
- Urdu (ur-**)
- Pashtu (ps-**)
- Syriac (syr-**)
- Divehi (dv-**)
- Hebrew (he-**)
- Yiddish (yi-**)