PHP xpath get elements by attribute in foreach loop - php

Question

im am trying to loop through all the LINE_ITEMS and it works fine but in the foreach-loop im trying to access the single LINE_ITEM by attribute by using xpath but i don't get any result. Does anyone know the problem ?
foreach($items = $xmlData->xpath('//zw:LINE_ITEM') as $item) {
$item->xpath('//namespace:PID[#type="erp_pid"]'); No result
}
$xmlData->xpath('//zw:LINE_ITEM')
works fine i get all LINE_ITEMS but
when i try to do some xpath on the item i don't get any result.
How can i access the PID value of for example "erp_pid" ?
<?xml version="1.0" encoding="UTF-8"?>
<NM_DOCS>
<NM_DOC>
<DOCUMENT qualifier="default" role="original" test="false" type="orders">
<VERSION>4.0</VERSION>
<HEADER>
<CONTROL_INFO>
<LAST_SAVE_DATE>2015-03-18T13:44:32+01:00</LAST_SAVE_DATE>
<PROCESS_TYPE>silent</PROCESS_TYPE>
<SOURCE>sales</SOURCE>
</CONTROL_INFO>
<SOURCING_INFO>
<REFERENCES>
<REFERENCE type="order_nexmart">
<ID>109546063</ID>
<DATES>
<DATE type="order">2015-03-18T13:44:30+01:00</DATE>
</DATES>
</REFERENCE>
</REFERENCES>
</SOURCING_INFO>
<DOCUMENT_INFO>
<DOCUMENT_ID>Test bestellnummer</DOCUMENT_ID>
<DATES>
<DATE type="delivery_ordered">2015-04-19T12:41:41+02:00</DATE>
</DATES>
<PARTIES>
<PARTY type="buyer">
<BUSINESS_ROLE>commercial</BUSINESS_ROLE>
<PORTAL_ID>BDE600028</PORTAL_ID>
<ADDITIONAL_IDS>
</ADDITIONAL_IDS>
<ADDRESS>
</ADDRESS>
<CONTACT_DETAILS>
<ACCOUNTS>
<ID type="emart">sales.nexmart</ID>
</ACCOUNTS>
</CONTACT_DETAILS>
</PARTY>
<PARTY type="supplier">
<BUSINESS_ROLE>commercial</BUSINESS_ROLE>
<PORTAL_ID>zweygart_app_de</PORTAL_ID>
<ADDITIONAL_IDS>
</ADDITIONAL_IDS>
<ADDRESS>
</ADDRESS>
<CONTACT_DETAILS>
</CONTACT_DETAILS>
</PARTY>
<PARTY type="delivery">
<BUSINESS_ROLE>commercial</BUSINESS_ROLE>
<ADDRESS>
</ADDRESS>
<CONTACT_DETAILS>
</CONTACT_DETAILS>
</PARTY>
<PARTY type="invoice_recipient">
<ADDRESS>
</ADDRESS>
<CONTACT_DETAILS>
</CONTACT_DETAILS>
</PARTY>
</PARTIES>
<REMARKS>
<REMARK type="order">Test bemerkung</REMARK>
</REMARKS>
</DOCUMENT_INFO>
</HEADER>
<LINE_ITEMS>
<LINE_ITEM>
<PRODUCT_ID>
<SUPPLIER_PID>119556</SUPPLIER_PID>
<GTIN>4030646269130</GTIN>
<ADDITIONAL_PIDS>
<PID type="supplier_pid_original">119556</PID>
<PID type="gtin_original">4030646269130</PID>
<PID type="erp_pid">119556</PID>
</ADDITIONAL_PIDS>
<DESCRIPTIONS>
<DESCR type="short">short desc</DESCR>
<DESCR type="short_original">some text</DESCR>
</DESCRIPTIONS>
</PRODUCT_ID>
</LINE_ITEM>
<LINE_ITEM>
<PRODUCT_ID>
<SUPPLIER_PID>123456789</SUPPLIER_PID>
<GTIN>123456789</GTIN>
<ADDITIONAL_PIDS>
<PID type="supplier_pid_original">123456</PID>
<PID type="gtin_original">123456</PID>
<PID type="erp_pid">123456</PID>
</ADDITIONAL_PIDS>
<DESCRIPTIONS>
<DESCR type="short">short desc</DESCR>
<DESCR type="short_original">Some description</DESCR>
</DESCRIPTIONS>
</PRODUCT_ID>
</LINE_ITEM>
</LINE_ITEMS>
</DOCUMENT>
</NM_DOC>
</NM_DOCS>

Answer 1

The problem is not XPath but SimpleXML. SimpleXMLElement::xpath() is limited. It converts the result into an array of SimpleXMLElement objects, but here are other nodes in a DOM. More important you will have to register the namespaces on each new SimpleXMLElement again.
$element = new SimpleXMLElement($xml);
$element->registerXPathNamespace('namespace', 'urn:foo');
foreach($element->xpath('//namespace:LINE_ITEMS/namespace:LINE_ITEM') as $item) {
$item->registerXPathNamespace('namespace', 'urn:foo');
var_dump((string)$item->xpath('.//namespace:PID[#type="erp_pid"]')[0]);
}
Output:
string(6) "119556"
string(6) "123456"
You might notice that I prefixed your detail expression with an .. A slash at the start of the expression always makes it relative to the document itself, not the current node. The . represents the current node.
If you use DOM directly, you create a separate DOMXPath object and register the namespaces on this object. Additionally you can use XPath expressions that return scalar values.
$dom = new DOMDocument();
$dom->loadXml($xml);
$xpath = new DOMXPath($dom);
$xpath->registerNamespace('namespace', 'urn:foo');
foreach($xpath->evaluate('//namespace:LINE_ITEMS/namespace:LINE_ITEM') as $node) {
var_dump($xpath->evaluate('string(.//namespace:PID[#type="erp_pid"])', $node));
}

Answer 2

This works for me:
foreach($xmlData->LINE_ITEM as $item) {
$erp = ( $item->xpath('//PID[#type="erp_pid"]'));
foreach($erp as $v) {
echo $v. " / ";
}
}
Just remove the namespace in your xpath, your xml doesn't use a namespace.
If you want to iterate through a part of the xml be sure to use the correct path.