'Node no longer exists' error in PHP - php

Question

I'm using the following code to turn user's IP into latitude/longitude information using the hostip web service:
//get user's location
$ip=$_SERVER['REMOTE_ADDR'];
function get_location($ip) {
$content = file_get_contents('http://api.hostip.info/?ip='.$ip);
if ($content != FALSE) {
$xml = new SimpleXmlElement($content);
$coordinates = $xml->children('gml', TRUE)->featureMember->children('', TRUE)->Hostip->ipLocation->children('gml', TRUE)->pointProperty->Point->coordinates;
$longlat = explode(',', $coordinates);
$location['longitude'] = $longlat[0];
$location['latitude'] = $longlat[1];
$location['citystate'] = '==>'.$xml->children('gml', TRUE)->featureMember->children('', TRUE)->Hostip->children('gml', TRUE)->name;
$location['country'] = '==>'.$xml->children('gml', TRUE)->featureMember->children('', TRUE)->Hostip->countryName;
return $location;
}
else return false;
}
$data = get_location($ip);
$center_long=$data['latitude'];
$center_lat=$data['longitude'];
This works fine for me, using $center_long and $center_lat the google map on the page is centered around my city, but I have a friend in Thailand who tested it from there, and he got this error:
Warning: get_location() [function.get-location]: Node no longer exists in /home/bedbugs/registry/index.php on line 21
So I'm completely confused by this, how could he be getting an error if I don't? I tried googling it and it has something to do with parsing XML data, but the parsing process is the same for me and him. Note that line 21 is the one that starts with '$coordinates =' .

Answer 1

You need to check the service actually has an <ipLocation> listed, you're doing:
$xml->children('gml', TRUE)->featureMember->children('', TRUE)->Hostip->ipLocation
->children('gml', TRUE)->pointProperty->Point->coordinates
but the XML output for my IP is:
<HostipLookupResultSet version="1.0.1" xsi:noNamespaceSchemaLocation="http://www.hostip.info/api/hostip-1.0.1.xsd">
<gml:description>This is the Hostip Lookup Service</gml:description>
<gml:name>hostip</gml:name>
<gml:boundedBy>
<gml:Null>inapplicable</gml:Null>
</gml:boundedBy>
<gml:featureMember>
<Hostip>
<ip>...</ip>
<gml:name>(Unknown City?)</gml:name>
<countryName>(Unknown Country?)</countryName>
<countryAbbrev>XX</countryAbbrev>
<!-- Co-ordinates are unavailable -->
</Hostip>
</gml:featureMember>
</HostipLookupResultSet>
The last part ->children('gml', TRUE)->pointProperty->Point->coordinates gives the error because it has no children (for some IPs).
You can add a basic check to see if the <ipLocation> node exists like this (assuming the service always returns at least up to the <hostIp> node):
function get_location($ip) {
$content = file_get_contents('http://api.hostip.info/?ip='.$ip);
if ($content === FALSE) return false;
$location = array('latitude' => 'unknown', 'longitude' => 'unknown');
$xml = new SimpleXmlElement($content);
$hostIpNode = $xml->children('gml', TRUE)->featureMember->children('', TRUE)->Hostip;
if ($hostIpNode->ipLocation) {
$coordinates = $hostIpNode->ipLocation->children('gml', TRUE)->pointProperty->Point->coordinates;
$longlat = explode(',', $coordinates);
$location['longitude'] = $longlat[0];
$location['latitude'] = $longlat[1];
}
$location['citystate'] = '==>'.$hostIpNode->children('gml', TRUE)->name;
$location['country'] = '==>'.$hostIpNode->countryName;
return $location;
}