Xpath query results are always empty - php

Question

I have the following XML document:
<?xml version="1.0"?>
<GetMatchingProductForIdResponse xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01">
<GetMatchingProductForIdResult Id="B0009VCOU4" IdType="ASIN" status="Success">
<Products xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01" xmlns:ns2="http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd">
<Product>
<Identifiers>
<MarketplaceASIN>
<MarketplaceId>ATVPDKIKX0DER</MarketplaceId>
<ASIN>B0009VCOU4</ASIN>
</MarketplaceASIN>
</Identifiers>
<AttributeSets>
<ns2:ItemAttributes xml:lang="en-US">
<ns2:Binding>Electronics</ns2:Binding>
<ns2:Brand>DOBANI</ns2:Brand>
<ns2:Feature>Handcrafted Quality, Value Priced</ns2:Feature>
<ns2:Feature>Satisfaction Guaranteed! 30-Day Return Policy!</ns2:Feature>
<ns2:ItemDimensions>
<ns2:Height Units="inches">7.00</ns2:Height>
<ns2:Length Units="inches">6.00</ns2:Length>
<ns2:Width Units="inches">6.00</ns2:Width>
</ns2:ItemDimensions>
<ns2:Label>Mid-East</ns2:Label>
<ns2:ListPrice>
<ns2:Amount>9.90</ns2:Amount>
<ns2:CurrencyCode>USD</ns2:CurrencyCode>
</ns2:ListPrice>
<ns2:Manufacturer>Mid-East</ns2:Manufacturer>
<ns2:Model>BULB</ns2:Model>
<ns2:PackageDimensions>
<ns2:Height Units="inches">3.70</ns2:Height>
<ns2:Length Units="inches">8.10</ns2:Length>
<ns2:Width Units="inches">4.00</ns2:Width>
<ns2:Weight Units="pounds">0.35</ns2:Weight>
</ns2:PackageDimensions>
<ns2:PackageQuantity>1</ns2:PackageQuantity>
<ns2:PartNumber>BULB</ns2:PartNumber>
<ns2:ProductGroup>Single Detail Page Misc</ns2:ProductGroup>
<ns2:ProductTypeName>MUSICAL_INSTRUMENTS</ns2:ProductTypeName>
<ns2:Publisher>Mid-East</ns2:Publisher>
<ns2:SmallImage>
<ns2:URL>http://ecx.images-amazon.com/images/I/31Fsu5jKWsL._SL75_.jpg</ns2:URL>
<ns2:Height Units="pixels">75</ns2:Height>
<ns2:Width Units="pixels">50</ns2:Width>
</ns2:SmallImage>
<ns2:Studio>Mid-East</ns2:Studio>
<ns2:Title>Spare Rubber Bulb</ns2:Title>
</ns2:ItemAttributes>
</AttributeSets>
<Relationships/>
<SalesRankings>
<SalesRank>
<ProductCategoryId>sdp_misc_display_on_website</ProductCategoryId>
<Rank>36468</Rank>
</SalesRank>
</SalesRankings>
</Product>
</Products>
</GetMatchingProductForIdResult>
<ResponseMetadata>
<RequestId>afnapq823haeufabq2rhalhtz</RequestId>
</ResponseMetadata>
</GetMatchingProductForIdResponse>
I am trying to get the package dimensions, but none of my xpath queries work. Have tried these using PHP's built-in xpath functions and using QueryPath 3.0.0, but neither works.
This doesn't work even though XML Tree in Chrome shows it should:
/GetMatchingProductForIdResponse/GetMatchingProductForIdResult/Products/Product/AttributeSets/ns2:ItemAttributes/ns2:PackageDimensions/ns2:Height
I thought neutralizing the namespace would get rid of the problem since the above triggers a namespace error, but it does not:
/GetMatchingProductForIdResponse/GetMatchingProductForIdResult/Products/Product/AttributeSets/*[local-name()='ItemAttributes']/*[local-name()='PackageDimensions']/*[local-name()='Height']

Answer 1

Xpath has no default namespace. The Xpath provided by Chrome is invalid. An Xpath element expression without a namespace prefix always matches elements without a namespace.
You need to register your own namespace prefixes and use them:
$dom = new DOMDocument();
$dom->loadXml($xml);
$xpath = new DOMXpath($dom);
$xpath->registerNamespace(
'p', 'http://mws.amazonservices.com/schema/Products/2011-10-01'
);
$xpath->registerNamespace(
'pd', 'http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd'
);
$result = $xpath->evaluate(
'string(
/p:GetMatchingProductForIdResponse
/p:GetMatchingProductForIdResult
/p:Products
/p:Product
/p:AttributeSets
/pd:ItemAttributes
/pd:PackageDimensions
/pd:Height
)'
);
var_dump($result);
Output: https://eval.in/150409
string(4) "3.70"

Answer 2

I'm afraid even the first part of your xpath is suffering for the namespace issue. Have you tried :
/*[local-name()='GetMatchingProductForIdResponse']/*[local-name()='GetMatchingProductForIdResult']/*[local-name()='Products']/*[local-name()='Product']/*[local-name()='AttributeSets']/*[local-name()='ItemAttributes']/*[local-name()='PackageDimensions']/*[local-name()='Height']
I think to use the normal xpath approach, you will need to set the corresponding namespaces on the xpath evaluator itsself.

Answer 3

/**
* Convert XML to JSON and return.
*/
$response = preg_replace("/(<\/?)(\w+):([^>]*>)/", "$1$2$3", $response);
$xml = simplexml_load_string($response);
$json = json_encode($xml);
return json_decode($json,TRUE);
This worked for me