$html = <<<'HTML'
<article>
<p rel="#" src="#">aaaaaa</p>
<p href="#" bla="#" bla2="#">bbbbbb</p>
</article>
HTML;
$dom = new DOMDocument;
@$dom->loadHTML($html, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
$xpath = new DomXPath($dom);
$elements = $xpath->query('//article/*');
$allowedAttributes = ['src', 'href'];
foreach($elements as $element) {
for( $i = $element->attributes->length; --$i >= 0; ) {
if( ! in_array( $element->attributes->item($i)->name, $allowedAttributes ) ) {
$element->removeAttribute($element->attributes->item($i)->name);
}
}
}
echo $dom->saveHTML();
https://3v4l.org/UPrsr
