How To Retrieve Comments From Within An XML Document

Question

I want to extract all comments below a specific node within an XML document, using PHP. I have tried both the SimpleXML and DOMDocument methods, but I keep getting blank outputs. Is there a way to retrieve comments from within a document without having to resort to Regex?

Answer 1

If you are using a SAX event driven-parser, the parser should have an event for comments. For example, when using Expat you would implement a handler and set it using:

void XMLCALL
XML_SetCommentHandler(XML_Parser p,
                      XML_CommentHandler cmnt);

Answer 2

Do you have access to an XPath API ? XPath allows you to find comments using (e.g.)

//comment()

Answer 3

SimpleXML cannot handle comments, but the DOM extension can. Here's how you can extract all the comments. You just have to adapt the XPath expression to target the node you want.

$doc = new DOMDocument;
$doc->loadXML(
    '<doc>
        <node><!-- First node --></node>
        <node><!-- Second node --></node>
    </doc>'
);

$xpath = new DOMXPath($doc);

foreach ($xpath->query('//comment()') as $comment)
{
    var_dump($comment->textContent);
}