Why does my script only the last H2 tag into the database?

I'm trying to store all the H2 tags into my database. I'm using Laravel 5.4 and DomDocument.

How i retrieve the h2 tags:

$htag2 = $dom->getElementsByTagName('h2');

My h2 tags:

<h2> htag2-1 </h2>
<h2> htag2-2 </h2>
<h2> htag2-3 </h2>
<h2> htag2-4 </h2>

This is the output in the database: htag2-4. As you can see it skips the other 3 h2tags in my xml file.

I'm trying to save this using for loop:

for ($i = 0; $i < $htag2->length; $i++) {
 $ts->h2_tag = $htag2->item($i)->nodeValue;
}

Declaration for $ts: $ts = new Scan;

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