SimpleXML returning multiple objects, how can I get the data?

问题

I'm using simpleXML to parse this xml file. It's a feed I'm using to access the YouTube API. I want to embed the most recent video in an object and display the next four thumbnails.

So I'm using simplexml_load_file on this, going using a foreach loop to access the values in each feed.

I can access the values no problem, but I run into the problem that it stores each video in a separate SimpleXMLElement Object. I don't have any control over which object I'm accessing as they are not stored in an array. So I can't get, say, $thumb[4] or $entry[4]->thumb.

I tried to use SimpleXMLIterator, but for whatever reason, any values that have the same beginning render as blank. For example, the video could have eleven variations of:

And these would each render as [1]="", [2]="", [3]="", etc.

I'll happily provide some more information to anyone who can help!

Edit

Here is the print_r of my results. This is done on a single variable to give you an idea of the structure issue I'm facing. The entire print_r($entry) would give variables for each node in the XML file.

SimpleXMLElement Object
(
    [0] => 159
)
SimpleXMLElement Object
(
    [0] => 44
)

Also, the print_r is simply inside the PHP block for testing. I'm actually looking to access the variables within echoes in the HTML.

回答1:

You ran into the problem of namespaces and SimpleXML. The feed starts with

<feed xmlns='http://www.w3.org/2005/Atom' xmlns:media='http://search.yahoo.com/mrss/' xmlns:openSearch='http://a9.com/-/spec/opensearchrss/1.0/' xmlns:gd='http://schemas.google.com/g/2005' xmlns:yt='http://gdata.youtube.com/schemas/2007'>

The xmlns='http://www.w3.org/2005/Atom' sets the default namespace to http://www.w3.org/2005/Atom. I.e. its child elements are not really id, updated, category but http://www.w3.org/2005/Atom:id, http://www.w3.org/2005/Atom:updated and so on...
So you can't access the the id element via $feed->id, you need the method SimpleXMLELement::children(). It lets you specify the namespace of the child elements you want to retrieve.

For example,

$feed = simplexml_load_file('http://gdata.youtube.com/feeds/api/videos?author=ofcoursegolf&max-results=5&prettyprint=true');
$children = $feed->children('http://www.w3.org/2005/Atom');
echo $children->updated;

Currently prints 2010-02-06T05:23:33.858Z.

To get the id of the first entry element you can use echo $children->entry[0]->id;.
But then you'll hit the <media:group> element and its children <media:category, <media:player> and so on..., which are in the xmlns:media='http://search.yahoo.com/mrss/' namespace.

$feed = simplexml_load_file('http://gdata.youtube.com/feeds/api/videos?author=ofcoursegolf&max-results=5&prettyprint=true');
$group = $feed->children('http://www.w3.org/2005/Atom')
  ->entry[0]
  ->children('http://search.yahoo.com/mrss/')
  ->group
  ->children('http://search.yahoo.com/mrss/')
;
echo $group->player->attributes()->url, "\n";
foreach( $group->thumbnail as $thumb) {
  echo 'thumb: ', $thumb->attributes()->url, "\n";
}

(Currently) prints

http://www.youtube.com/watch?v=ikACkCpJ-js&feature=youtube_gdata
thumb: http://i.ytimg.com/vi/ikACkCpJ-js/2.jpg
thumb: http://i.ytimg.com/vi/ikACkCpJ-js/1.jpg
thumb: http://i.ytimg.com/vi/ikACkCpJ-js/3.jpg
thumb: http://i.ytimg.com/vi/ikACkCpJ-js/0.jpg

Edit: I'd probably do that within the browser with a lot more JavaScript, but here's a (simple, ugly) example app.

<?php
//define('TESTENV' , true);
function getFeed($author) {
  // <-- add caching here if needed -->
  if ( !defined('TESTENV') ) {
    $url = sprintf('http://gdata.youtube.com/feeds/api/videos?author=%s&max-results=5',
      urlencode($author)
    );
  }
  else {
    $url = 'feed.xml';
  }
  return simplexml_load_file($url);
}
$feed = getFeed('jonlajoie');

if ( !isset($_GET['id']) ) {
  $selected = '';
}
else {
  $selected =  $_GET['id'];
  printf ('
    <object width="425" height="344">
      <param name="movie" value="http://www.youtube.com/v/%s"></param>
      <param name="allowFullScreen" value="true"></param>
      <param name="allowscriptaccess" value="always">
      </param>
      <embed src="http://www.youtube.com/v/%s" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed>
    </object>',
    htmlspcialchars($selected), htmlspcialchars($selected)
  );
}

$item = 0;
foreach( $feed->children('http://www.w3.org/2005/Atom')->entry as $entry ) {
  $entryElements = $entry->children('http://www.w3.org/2005/Atom');
  $groupElements = $entry
    ->children('http://search.yahoo.com/mrss/')
    ->group
    ->children('http://search.yahoo.com/mrss/')
  ;

  if ( !preg_match('!^http://gdata.youtube.com/feeds/api/videos/([^/]+)!', $entryElements->id, $m) ) {
    // google can choose whatever id they want. But this is only a simple example....
    die('unexpected id: '.htmlspecialchars($entryElements->id));
  }
  $id = $m[1];
  if ( $selected!==$id ) {
    printf('<a href="?id=%s"><img src="%s" /></a>',
      urlencode($id),
      $groupElements->thumbnail[0]->attributes()->url
    );
  }
}

Edit 2: "And when I click the thumbnails, I'll use jQuery to load the video in the main space. Seems like I'll need precise access to node[#], right?"
If you're already using JavaScript/jQuery your PHP script (if needed at all) could simply return a (JSON encoded) array of all the data for all the video and your jQuery script could figure out what to do with the data.

回答2:

$doc = new DOMDocument();
$doc->loadXML(file_get_contents('http://gdata.youtube.com/feeds/api/videos?author=ofcoursegolf&max-results=5&prettyprint=true'));
$xpd = new DOMXPath($doc);
$xpd->registerNamespace('atom', "http://www.w3.org/2005/Atom");
false&&$node = new DOMElement();//this is for my IDE to have intellysense

$result = $xpd->query('//atom:feed/atom:entry[1]/media:group/media:thumbnail');
foreach($result as $node){
    echo $node->getAttribute('url').'<br />';
}

echo "more results <br />";
$result = $xpd->query('//atom:feed/atom:entry[1]/media:group/media:thumbnail[1]');
foreach($result as $node){
    echo $node->getAttribute('url').'<br />';
}

回答3:

Try $sxml->entry[4]->thumb or something to that regard.

AKA, to access the first entries ID, you would go $sxml->entry[4]->id

Basically $sxml->entry is an array of SimpleXMLElement Objects. When you foreach them, you are going through each object and assigning it to $entry, so that $entry = $sxml->entry[0] and upwards.

You can go like this:

print_r($sxml);

to see the ENTIRE structure. And that will tell you what you need to use to access it.

回答4:

In the end, I did two foreach loops, one running through an XML feed showing the most recent one entry. Then, I echoed out the object around this to play the vide.

In the other, I ran through the most recent four entries, returning list elements for a list of thumbnails.

Now, when I click on a thumbnail video, javascript handles passing the parameters to the main entry. Now, how to reload that main object upon receiving the parameters, I'm open to ideas.

来源：https://stackoverflow.com/questions/2212009/simplexml-returning-multiple-objects-how-can-i-get-the-data

标签

php

xml

simplexml

youtube-api