PHP DOM Document - get everything between two nodes - php

Question

I have this as a part of my XML that I am loading in a DOM Document:
<error n='\Author'/>
Some Text 1
<formula type='inline'><math xmlns='http://www.w3.org/1998/Math/MathML'><msup><mrow/> <mrow><mn>1</mn><mo>,</mo></mrow> </msup></math></formula>
Some Text 2
<formula type='inline'><math xmlns='http://www.w3.org/1998/Math/MathML'><msup><mrow/> <mn>2</mn> </msup></math></formula>
<error n='\address' />
My goal is to get everything as nodeValue between the
<error n='\Author' />
And
<error n='\address' />
How can this be done?
I tested this:
$author_node = $xpath_xml->query("//error[#n='\Author']/following-sibling::*[1]")->item(0);
if ($author_node != null) {
$i = 1;
$nextNodeName = "";
$author = "";
while ($nextNodeName != "error" && $i < 20) {
$nextNodeName = $xpath_xml->query("//error[#n='\Author']/following-sibling::*[$i]")->item(0)->tagName;
if ($nextNodeName == "error")
continue;
$author .= $nextNode->nodeValue;
}
But Am getting only the formula content, not the text between formulas.
Thank you.

Answer 1

The *only selects element nodes, not text nodes. So only the <formula> elements are selected. You need to use node(). But you could use xpath directly to selected the needed nodes. Look for an explanation of the Kayessian method.
$dom = new DOMDocument();
$dom->loadXml($xml);
$xpath = new DOMXpath($dom);
$nodes = $xpath->evaluate(
'//error[#n="\\Author"][1]
/following-sibling::node()
[
count(
.|
//error[#n="\\Author"][1]
/following-sibling::error[#n="\\address"][1]
/preceding-sibling::node()
)
=
count(
//error[#n="\\Author"][1]
/following-sibling::error[#n="\\address"][1]
/preceding-sibling::node()
)
]'
);
$result = '';
foreach ($nodes as $node) {
$result .= $node->nodeValue;
}
var_dump($result);
Demo: https://eval.in/125494
If you want to save not only the text content, but the XML fragment, you can use DOMDocument::saveXml() with the node as argument.
$result = '';
foreach ($nodes as $node) {
$result .= $node->ownerDocument->saveXml($node);
}
var_dump($result);