How may I get the id of a div, or any other div information during the save_post hook?

I have a div with inputs within it in my document, and I would like to be able to save more than just each input’s value in a function, run during the save_post hook. for testing, it looks like this at the moment:

$sanitized_data = array();
foreach ( $resources as $index=>$resource ) {
    $resource = esc_url( strip_tags( $resource ) );
    if ( ! empty( $resource ) ) {
        $sanitized_data[$index] = $resource;
    }
}

$myDocument->update_post_meta(
    $post_id,
    'Meta_key',
    $sanitized_data
);

I’m not sure how to retrieve any other information, and I suspect when the save_post action is run the document no longer exists, only the meta data, or at least that’s the way it seems.

I created this function to try and see what was going on:

$elements = $this->getElementsByTagName('input_wrapper');

foreach($elements as $index=>$child) {
    var_dump( $child );
}
die();

Unfortunately, this comes up with nothing but a blank screen. Can anyone help me?