Finding value of nodes using XMLDOm in PHP - php

Question

I need to extract information from an XML using XMLDom.
Below is myroot.xml
<?xml version='1.0' encoding='ISO-8859-1'?>
<myroot xml:lang='en'>
<delta>
<history>
<detail>
<id>one</id>
<degree>
<dname>alpha</dname>
<dates>
<StartDate>
<Year>1998</Year>
</StartDate>
<EndDate>
<Year>2002</Year>
</EndDate>
</dates>
</degree>
</detail>
<detail>
<id>two</id>
<degree>
<dname>beta</dname>
<dates>
<StartDate>
<Year>2006</Year>
</StartDate>
<EndDate>
<Year>2008</Year>
</EndDate>
</dates>
</degree>
</detail>
</history>
</delta>
here is my code
$doc = new DOMDocument;
$doc->preserveWhiteSpace = false;
$rootxmldoc = $doc->load('myroot.xml');
$xpath = new DOMXPath($rootxmldoc);
$items = $hrxml_obj->getElementsByTagName("detail");
$subitemarray = array();
$icounter = 0;
foreach ($items as $item) {
$query = "//dates/*/Year"; //xpath of all occurrence of Year
$entries = $xpath->query($query, $item);
foreach ($entries as $entry) {
$dates["startdate"] = "todo"; //extract StartDate
$dates["enddate"] = "todo"; //extract EndDate
}
$subitemarray[$icounter++] = dates;
}
var_dump($subitemarray);
Ideally I need to extract dates using xpath. I am not able to get this nailed. any help is appreciated. The issue is the usage of xpath while looping.

Answer 1

With XPath go directly to yout dates tag, and then use DOMElement::getElementsByTagName() to get StartDate and EndDate (you can also go to the dates tag using DOMDocument::getElementsByTagName(), but XPath gives you more flexibility should you need it). This will return a DOMNodeList, but you know (if the structure is constant) that you only need the first element of the list. So:
// $xml ommited, saved in a variable for testing purposes
$doc = new DOMDocument;
$doc->preserveWhiteSpace = false;
$doc->loadXML($xml);
$xpath = new DOMXPath($doc);
$items = $doc->getElementsByTagName("detail");
$subitemarray = array();
$icounter = 0;
foreach ($items as $item) {
$query = "//dates"; //xpath of all occurrence of Year
$entries = $xpath->query($query, $item);
foreach ($entries as $entry) {
$startDate = $entry->getElementsByTagName("StartDate")[0]->nodeValue;
$endDate = $entry->getElementsByTagName("EndDate")[0]->nodeValue;
$dates["startdate"] = $startDate; //extract StartDate
$dates["enddate"] = $endDate; //extract EndDate
}
$subitemarray[$icounter++] = $dates;
}
var_dump($subitemarray);
Demo
Or only with XPath:
$doc = new DOMDocument;
$doc->preserveWhiteSpace = false;
$doc->loadXML($xml);
$xpath = new DOMXPath($doc);
$items = $doc->getElementsByTagName("detail");
$subitemarray = array();
$icounter = 0;
foreach ($items as $item) {
$queryStart = "//dates/StartDate";
$entriesStart = $xpath->query($queryStart, $item);
$dates["startdate"] = $entriesStart[0]->nodeValue;
$queryEnd = "//dates/EndDate";
$entriesEnd = $xpath->query($queryEnd, $item);
$dates["enddate"] = $entriesEnd[0]->nodeValue;
$subitemarray[$icounter++] = $dates;
}
var_dump($subitemarray);
And lastly, using only one XPath query:
$doc = new DOMDocument;
$doc->preserveWhiteSpace = false;
$doc->loadXML($xml);
$xpath = new DOMXPath($doc);
$items = $doc->getElementsByTagName("detail");
$subitemarray = array();
$icounter = 0;
foreach ($items as $item) {
$query = "//dates/*[contains(local-name(), 'Date')]
";
$entries = $xpath->query($query, $item);
$dates["startdate"] = $entries[0]->nodeValue;
$dates["enddate"] = $entries[1]->nodeValue;
$subitemarray[$icounter++] = $dates;
}
var_dump($subitemarray);
Demo
The query will simply get any elements inside the current detail element that contains the word "Date". Again, if the structure is constant, you can assume that the first result will be StartDate and the second result will be EndDate.