If the <a href="[..]">
ist just the outer element, you can do it like this:
$heading['h2']=$html->find('a h2');
foreach ($heading['h2'] as $h2) {
echo $h2->parent(), "\n";
}
You could also go up the DOM tree until you reach an <a>
tag:
$heading['h2']=$html->find('a h2');
foreach ($heading['h2'] as $h2) {
$a = $h2;
while ($a && $a->tag != "h2") $a = $a->parent();
if (!$a) continue; // no <a> above <h2>
echo $a, "\n";
}