PHP script to echo VLC now playing XML attributes

问题

I've been searching for a while on this and haven't had much luck. I've found plenty of resources showing how to echo data from dynamic XML, but I'm a PHP novice, and nothing I've written seems to grab and print exactly what I want, though from everything I've heard, it should be relatively easy. The source XML (located at 192.168.0.15:8080/requests/status.xml) is as follows:

<root>
  <fullscreen>0</fullscreen>
  <volume>97</volume>
  <repeat>false</repeat>
  <version>2.0.5 Twoflower</version>
  <random>true</random>
  <audiodelay>0</audiodelay>
  <apiversion>3</apiversion>
  <videoeffects>
  <hue>0</hue>
  <saturation>1</saturation>
  <contrast>1</contrast>
  <brightness>1</brightness>
  <gamma>1</gamma>
  </videoeffects>
  <state>playing</state>
  <loop>true</loop>
  <time>37</time>
  <position>0.22050105035305</position>
  <rate>1</rate>
  <length>168</length>
  <subtitledelay>0</subtitledelay>
  <equalizer/>
  <information>
  <category name="meta">
  <info name="description">
  000003EC 00000253 00000D98 000007C0 00009C57 00004E37 000068EB 00003DC5 00015F90 00011187
  </info>
  <info name="date">2003</info>
  <info name="artwork_url"> file://brentonshp04/music%24/Music/Hackett%2C%20Steve/Guitar%20Noir%20%26%20There%20Are%20Many%20Sides%20to%20the%20Night%20Disc%202/Folder.jpg
  </info>
  <info name="artist">Steve Hackett</info>
  <info name="publisher">Recall</info>
  <info name="album">Guitar Noir &amp; There Are Many Sides to the Night Disc 2
  </info>
  <info name="track_number">5</info>
  <info name="title">Beja Flor [Live]</info>
  <info name="genre">Rock</info>
  <info name="filename">Beja Flor [Live]</info>
  </category>
  <category name="Stream 0">
  <info name="Bitrate">128 kb/s</info>
  <info name="Type">Audio</info>
  <info name="Channels">Stereo</info>
  <info name="Sample rate">44100 Hz</info>
  <info name="Codec">MPEG Audio layer 1/2/3 (mpga)</info>
  </category>
  </information>
  <stats>
  <lostabuffers>0</lostabuffers>
  <readpackets>568</readpackets>
  <lostpictures>0</lostpictures>
  <demuxreadbytes>580544</demuxreadbytes>
  <demuxbitrate>0.015997290611267</demuxbitrate>
  <playedabuffers>0</playedabuffers>
  <demuxcorrupted>0</demuxcorrupted>
  <sendbitrate>0</sendbitrate>
  <sentbytes>0</sentbytes>
  <displayedpictures>0</displayedpictures>
  <demuxreadpackets>0</demuxreadpackets>
  <sentpackets>0</sentpackets>
  <inputbitrate>0.016695899888873</inputbitrate>
  <demuxdiscontinuity>0</demuxdiscontinuity>
  <averagedemuxbitrate>0</averagedemuxbitrate>
  <decodedvideo>0</decodedvideo>
  <averageinputbitrate>0</averageinputbitrate>
  <readbytes>581844</readbytes>
  <decodedaudio>0</decodedaudio>
  </stats>
  </root>

What I'm trying to write is a simple PHP script that echoes the artist's name (In this example Steve Hackett). Actually I'd like it to echo the artist, song and album, but I'm confident that if I'm shown how to retrieve one, I can figure out the rest on my own.

What little of my script which actually seems to work goes as follows. I've tried more than what's below, but I left out the bits that I know for a fact aren't working.

<?PHP
$file = file_get_contents('http://192.168.0.15:8080/requests/status.xml');
$sxe = new SimpleXMLElement($file);

foreach($sxe->...

echo "Artist: "...

?>

I think I need to use foreach and echo, but I can't figure out how to do it in a way that will print what's between those info brackets.

I'm sorry if I've left anything out. I'm not only new to PHP, but I'm new to StackOverflow too. I've referenced this site in other projects, and it's always been incredibly helpful, so thanks in advance for your patience and help!

////////Finished Working Script - Thanks to Stefano and all who helped!

<?PHP
$file = file_get_contents('http://192.168.0.15:8080/requests/status.xml');
$sxe = new SimpleXMLElement($file);

$artist_xpath = $sxe->xpath('//info[@name="artist"]');
$album_xpath = $sxe->xpath('//info[@name="album"]');
$title_xpath = $sxe->xpath('//info[@name="title"]');


$artist = (string) $artist_xpath[0];
$album = (string) $album_xpath[0];
$title = (string) $title_xpath[0];


echo "<B>Artist: </B>".$artist."</br>";
echo "<B>Title: </B>".$title."</br>";
echo "<B>Album: </B>".$album."</br>";
?>

回答1:

Instead of using a for loop, you can obtain the same result with XPath:

// Extraction splitted across two lines for clarity
$artist_xpath = $sxe->xpath('//info[@name="artist"]');
$artist = (string) $artist_xpath[0];
echo $artist;

You will have to adjust the xpath expression (i.e. change @name=... appropriately), but you get the idea. Also notice that [0] is necessary because xpath will return an array of matches (and you only need the first) and the cast (string) is used to extract text contained in the node.

Besides, your XML is invalid and will be rejected by the parser because of the literal & appearing in the <info name="album"> tag.

回答2:

If you look at your code again, you are missing a function that turns the first result of the xpath expression into a string of a SimpleXMLElement (casting).

One way to write this once is to extend from SimpleXMLElement:

class BetterXMLElement extends SimpleXMLElement
{
    public function xpathString($expression) {
        list($result) = $this->xpath($expression);
        return (string) $result;
    }
}

You then create the more specific SimpleXMLElement like you did use the less specific before:

$file = file_get_contents('http://192.168.0.15:8080/requests/status.xml');
$sxe  = new BetterXMLElement($file);

And then you benefit in your following code:

$artist = $sxe->xpathString('//info[@name="artist"]');
$album  = $sxe->xpathString('//info[@name="album"]');
$title  = $sxe->xpathString('//info[@name="title"]');

echo "<B>Artist: </B>".$artist."</br>";
echo "<B>Title: </B>".$title."</br>";
echo "<B>Album: </B>".$album."</br>";

This spares you some repeated code. This means as well less places you can make an error in :)

Sure you can further on optimize this by allowing to pass an array of multiple xpath queries and returning all values named then. But that is something you need to write your own according to your specific needs. So use what you learn in programming to make programming more easy :)

If you want some more suggestions, here is another, very detailed example using DOMDocument, the sister-library of SimpleXML. It is quite advanced but might give you some good inspiration, I think something similar is possible with SimpleXML as well and this is probably what you're looking for in the end:

Extracting data from HTML using PHP and xPath

来源：https://stackoverflow.com/questions/16498059/php-script-to-echo-vlc-now-playing-xml-attributes

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xml

vlc