php parse html data from specific positions - php

Question

I have a lot of these in my html document:
<div class="thumb-under">
<p class="title">
text
</p>
<p class="metadata">
<span class="bg">
<span class="first">3A
</span>
<a href="4A">
<span class="name">5A
</span></a>
<span>
<span class="spring"> -
</span> 6A
<span class="spring">something
</span>
</span>
<span class="spring"> -
</span>
</span>
</p>
</div>
so I need to extract data from positions 1A, 2A, 3A, 4A, 5A, 6A
I tried this but something I am doing wrong:
$matches = array();
$dom = new DOMDocument;
$dom->loadHTML($html);
foreach($dom->getElementsByTagName('p') as $tr) {
if ( ! $tr->hasAttribute('class')) {
continue;
}
$class = explode(' ', $tr->getAttribute('class'));
if (in_array('title', $class)) {
$matches[] = $tr->getElementsByTagName('a');
}
}
print_r($matches);
I am totally lost...