SimpleXML and PHP XPath expression not returning correct data

Shouldn't the xpath be:

/achievements/category/achievement[@id='4602']

Or:

//category/achievement[@id='4602']

http://www.w3schools.com/xpath/xpath_syntax.asp

Update:

The issue with that code is the fact that you were adding <br /> to the end of each name in $array. Generally, avoid adding formatting in this way, unless there's a good reason.

Also, note my notes in the comments. Especially, urlendcode(). I left this for you to do with $url as I didn't notice it until after starting this edit and I'm lazy. ;) Note, that once you pass those query string params through urlencode() the + in the guild name won't be necessary and it will actually get in the way.

ini_set("user_agent", "Mozilla/5.0 (X11; U; Linux i686; pl-PL; rv:1.9.0.2) Gecko/20121223 Ubuntu/9.25 (jaunty) Firefox/3.8");

$server = "Sunstrider";
$guild = "Operation+Eskimo";

$url='http://eu.wowarmory.com/guild-info.xml?r='.$server.'&gn='.$guild;
$xml = simplexml_load_file($url);

$array = array();

foreach ($xml->guildInfo->guild->members->character as $char)
{
    if (strtolower($char['level']) === '80')
    {
        $array[] = $char['name'];
    }
}

foreach ($array as $i => $name)
{
// note that this if statement and $i in the foreach are only here to limit this to 1 for testing, the full list spews out A LOT of data and takes A LONG time
if ($i) 
{
exit;
}
    // note the urlencode() call, that's important
    $raidurl='http://eu.wowarmory.com/character-achievements.xml?r=' . urlencode($server) . '&cn=' . urlencode($name) . '&c=168';
    $xmlraid = simplexml_load_file($raidurl);

    // note the pre tags around var_dump, makes things easier to read in the browser
    // also note print instead of echo, I lke to do this for debugging, as it makes 
    // it easier to determine what's is debug output for those long running debugging sessions
    print '<pre>';
    var_dump($xmlraid);
    print '</pre>';
     echo "<br><br>";

    // quick and dirty solution for viewing the XML
    /*print '<textarea cols="400" rows="2000">';
    print $xmlraid->asXML();
    print '</textarea>';*/

    $achievement = $xmlraid->xpath("/achievements/category/achievement[@id='4602']");

    print '<pre>';
    var_dump($achievement);
    print '</pre>';
}

No, check the doc. simplexml_load_file() returns an object representing the XML into $xmlraid. I suggest doing a var_dump($xmlraid); and to verify your xpath expression.

The document element is achievements.

Your XPATH statement should be:

/achievements/category/achievement[id='4602']

Damn, those people are nasty browser-sniffers. I didn't do it all in vain though, this works:

<?php
$opts = array(
    'http' => array(
        'header' => 'User-Agent: Firefox/3.5.9\r\n'
    )
);
$context = stream_context_create($opts);
libxml_set_streams_context($context);

$d = simplexml_load_file('http://eu.wowarmory.com/character-achievements.xml?r=Sunstrider&cn=Secrezy&c=168');
var_dump($d->xpath("//achievement[@id='4602']"));

The __extremely_ sad thing is, at first I just hoped it would be at least Accept or at the most Accept-Encoding - headers. But no, the "shouldn't mean anything significant"-User-Agent-header. A fine example why browser sniffing is bad if I ever saw one.