Xpath in PHP with OTA standards - php

Question

I have basic knowledge about the use of Xpath in PHP, but I'm having some troubles with a specific case and I think that the problem is in the standards.
This is the snippet of the XML and it's based on the OTA standards:
<SendHotelResResult xmlns:a="http://schemas/Models/OTA" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
<a:RoomRates>
<a:RoomRate>
<a:EffectiveDate>2015-11-13T00:00:00</a:EffectiveDate>
<a:ExpireDate>2015-11-15T00:00:00</a:ExpireDate>
<a:RatePlanID>25</a:RatePlanID>
<a:RatesType>
<a:Rates>
<a:Rate>
<a:AgeQualifyingCode i:nil="true"/>
<a:EffectiveDate>2015-11-13T00:00:00</a:EffectiveDate>
<a:Total>
<a:AmountAfterTax>0</a:AmountAfterTax>
<a:AmountBeforeTax>260.00</a:AmountBeforeTax>
<a:CurrencyCode>EUR</a:CurrencyCode>
</a:Total>
</a:Rate>
<a:Rate>
<a:AgeQualifyingCode i:nil="true"/>
<a:EffectiveDate>2015-11-14T00:00:00</a:EffectiveDate>
<a:Total>
<a:AmountAfterTax>0</a:AmountAfterTax>
<a:AmountBeforeTax>260.00</a:AmountBeforeTax>
<a:CurrencyCode>EUR</a:CurrencyCode>
</a:Total>
</a:Rate>
</a:Rates>
</a:RatesType>
<a:RoomID>52</a:RoomID>
<a:Total>
<a:AmountAfterTax>546.00</a:AmountAfterTax>
<a:AmountBeforeTax>520.00</a:AmountBeforeTax>
<a:CurrencyCode>EUR</a:CurrencyCode>
</a:Total>
</a:RoomRate>
</a:RoomRates>
</SendHotelRes>
What I want:
Get a specific <RoomRate> tag based on the element <RoomID>.
Get the global RoomRate <Total> tag. I don't want the <Total> tag that is inside the <Rate> tag. This is the reason why I'm using the xpath rather than a simple getElementsByTagName('Total'). I don't know if the OTA standards has some approach to differentiate the Total tags.
My attempts until now:
$dom = new DOMDocument();
$response = $dom->load($xmlSendHotelRes);
$roomID = '52';
$roomRatesTag = $response->getElementsByTagName('RoomRates')->item(0);
$prefix = $roomRatesTag->prefix;
$namespace = $roomRatesTag->lookupNamespaceURI($prefix);
$xpath = new DOMXpath($dom);
$xpath->registerNamespace($prefix, $namespace);
$roomRateTotal = $xpath->query("//RoomRate[RoomID=$roomID]/Total", $roomRatesTag, true);
I already tried with and without $roomRatesTag as context and also other expressions like:
./RoomRate[RoomID=$roomID]/Total, //RoomRate[RoomID=$roomID]/Total, //RoomRate/[RoomID=$roomID]/Total,//RoomRate[RoomID=$roomID]/Total and //RoomRate/RoomID[text() = $roomID]/../Total but any of them works.
Actually, even $roomRate = $xpath->query("//RoomRate"); returns a empty DOMNodeList, so, I don't know what I doing wrong and I'm thinking about the problem in the standards with 2 identical tags in different places, although this not make much sense.
Are there some other expressions that I need to try?

Answer 1

You're fetching the namespace from the document.
$prefix = $roomRatesTag->prefix;
$namespace = $roomRatesTag->lookupNamespaceURI($prefix);
But this is not necessary or a good idea. You know that the document uses OTA, so you know the namespace is http://schemas/Models/OTA.
The prefix is just an alias for the actual namespace value the following 3 XML example all resolve to a node {http://schemas/Models/OTA}RoomRates
<a:RoomRates xmlns:a="http://schemas/Models/OTA"/>
<ota:RoomRates xmlns:ota="http://schemas/Models/OTA"/>
<RoomRates xmlns="http://schemas/Models/OTA"/>
Your Api has to look for nodes inside the namespace.
One possibility is to use the *NS (namespace aware) methods.
$response->getElementsByTagNameNS('http://schemas/Models/OTA', 'RoomRates')->item(0);
The other is to use Xpath and register prefixes for the namespaces. This can be the prefixes from the document, or different ones.
$document = new DOMDocument();
$document->load($xmlSendHotelRes);
$xpath = new DOMXpath($document);
$xpath->registerNamespace('ota', 'http://schemas/Models/OTA');
var_dump(
$xpath->evaluate(
'string(//ota:RoomRates/ota:RoomRate[ota:RoomID=$roomID]/ota:Total)')
)
);
For a location path, DOMXpath::evaluate() would return a DOMNodeList but with string() it casts the first found node into a string and returns it.

Answer 2

You need to use a prefix (that you registered) and I think you want to start your path with .// and not with // if you want to search relative to the context node, so try ".//a:RoomRate[a:RoomID=$roomID]/a:Total"