Xpath - how control every element value with others?

Question

EXAMPLE:
My XML:

<root>
    <a>
        <b>1</b>
        <b>1</b>
        <b>2</b>
    </a>
    <a>
        <b>1</b>
        <b>2</b>
    </a>
    <a>
        <b>1</b>
    </a>
</root>

• A now, how to control that every "b" element has got only the same one value(not only "1")?
• Is it possible? I found only, but it doesnt work: //a/b != ./b
• I have no idea except some loop or count by value in element ... but it cant in xpath, or not?

Thanks for replies.

Answer 1

To get the number of different values for all /*/a/b element nodes, you can count the distinct values of those elements:

count(/*/a/b[not(. = preceding::b)])

This expression will return 1 if there is one distinct value, 2 if two (as in your case) or 0 if there are no /*/a/b elements in the document.

PHP Example:

<?php

$buffer = <<<XML
<root>
    <a>
        <b>1</b>
        <b>1</b>
        <b>2</b>
    </a>
    <a>
        <b>1</b>
        <b>2</b>
    </a>
    <a>
        <b>1</b>
    </a>
</root>
XML;

$doc = new DOMDocument();
$doc->loadXML($buffer);
$xpath = new DOMXPath($doc);

echo $xpath->evaluate('count(/*/a/b[not(. = preceding::b)])');  # echoes 2