XML php get xpath next node from loop or how to loop from xpath parents

I have xml

<tag>
        <id>106</id>
        <title>DG</title>
</tag>
<tag>
        <id>1</id>
        <title>DjG</title>
</tag>

I use this code

$dom = new DomDocument();
$dom->loadXml($xml);
$xpath = new DOMXPath($dom);
echo count($xpath->evaluate('//tag/*'));
foreach ($xpath->evaluate('//tag/*') as $i=>$node) {
  echo  $xpath->evaluate('local-name(parent::*)', $node) . "=" .$i . "\n";
}

I cant get each tag node and get all childrens something like this

1 tag=1 tag=2 tag=3 tag=4

but how to get

2

tag=1 tag=2

and how to count tags and print_r($node) each node?