use of not in xpath query - php

Question

i am fetching specific data from a site for which i am using XPath but for this i have to exclude few variables for which i have to use NOT. but this NOT is not working in the code please explain what i have to do to make it work :
heres the html code
<tr><td colspan="2" valign="top" align="left"><span class="tl-document">
<left>some text here
</left>
</span></td></tr>
<tr><td colspan="2" valign="top" align="left">
<span class="text-id">some text here,<sup>a</sup><sup>b</sup></span>
<span class="text-id">some text here,<sup>a</sup></span>
</td></tr>
<tr><td colspan="2" valign="top" class="right">
<sup>a</sup>some text here<br>
</td></tr>
<tr><td colspan="2" valign="top" class="right">
<sup>b</sup>some text here<br>
</td></tr>
<td colspan="2" valign="top">
<br><div>
<span class="tl-default">Objective</span>
<p>some text here,</p>
</div>
<div>
<span class="tl-default">Methods</span>
<p>some text here,</p>
</div>
<div>
</td>
<td colspan="2" valign="top">
<br><div>
<span class="tl-default">Objective</span>
<p>some text here,</p>
</div>
</td>
trying to fetch only not td containing class and align and for this i am using this method for my xpath :
$getnew="http://www.example.com/;
$html = new DOMDocument();
#$html->loadHtmlFile($getnew);
$xpath = new DOMXPath( $html );
$y = $xpath->query('//td[#colspan="2" and valign="top" and (not(#class and #align))]');
$ycnt = $y->length;
for ( $idf=6; $idf<$ycnt; $idf++)
{ if($idf==6){
echo "<p class='artbox'>".$y->item($idf)->nodeValue."</p>";}
}
i am new to this so please suggest your opinions

Answer 1

The problem with your logic is that no elements have both #class and #align, so the not() will always yield true.
Instead you should exclude elements that have either attribute:
//td[#colspan="2" and #valign="top" and not(#class or #align)]
Alternatively, to match elements that only have those two attributes, you can add a count() condition:
//td[#colspan="2" and #valign="top" and count(#*)=2]
Update
$query = '//td[#colspan="2" and #valign="top" and not(#class or #align)]';
foreach ($xpath->query($query) as $node) {
// do something with $node
}