Question

I am trying to access a specific element of the Dom using XPath

Here is an example

<table>
<tbody>
    <tr>
        <td>
            <b>1</b> <a href="http://www.url.html">data</a><br>
            <b>2</b> <a href="http://www.url.html">data</a><br>
            <b>3</b> <a href="http://www.url.html">data</a><br>
        </td>
    </tr>
</tbody>
</table>

I want to target “table td” so my query in Xpath is something like

$finder->query('//table/td');

only this doesn’t return the td as its a sub child and direct access would be done using

$finder->query('//tr/td');

Is there a better way to write the query which would allow me to use something like the first example ignoring the elements in-between and return the TD?

Answer 1

Is there a better way to write the query which would allow me to use
something like the first example ignoring the elements in-between and
return the TD?

You can write:

//table//td

However, is this really “better”?

In many cases the evaluation of the XPath pseudo-operator // can result in significant inefficiency as it causes the whole subtree rooted in the context-node to be traversed.

Whenever the path to the wanted nodes is statically known, it may be more efficient to replace any // with the specific, known path, thus avoiding the complete subtree traversal.

For the provided XML document, such expression is:

/*/*/tr/td

If there is more than one table element, each a child of the top element and we want to select only the tds of the forst table, a good, specific expression is:

/*/table[1]/*/tr/td

If we want to select only the first td of the first table in the same document, a good way to do this would be:

(/*/table[1]/*/tr//td)[1]

Or if we want to select the first td in the XML document (not knowing its structure in advance), then we could specify this:

(//td)[1]