Fetch image from html content

pgmb_content_img.php

<?php

function pgmb_insert_content_img($localPost, $post_id, $is_autopost, $location){
	if(
		!class_exists('DOMDocument') ||
		!class_exists('\PGMB\Google\MediaItem')
	){ return $localPost; }

	$form_fields = get_post_meta($post_id, 'mbp_form_fields', true);

	if(!isset($form_fields['mbp_content_image']) || !empty($form_fields['mbp_post_attachment'])){
		return $localPost;
	}

	$parent_post_id = wp_get_post_parent_id($post_id);

	$parent_post = get_post($parent_post_id);

	$doc = new DOMDocument();
	@$doc->loadHTML($parent_post->post_content);

	$tags = $doc->getElementsByTagName('img');

	if(empty($tags)){ return $localPost; }

	foreach($tags as $tag){
		$first_image_src = $tag->getAttribute('src');
		break;
	}
	if(!isset($first_image_src)){ return $localPost; }

	$mediaItem = new \PGMB\Google\MediaItem('PHOTO', $first_image_src);

	$localPost->addMediaItem($mediaItem);

	return $localPost;

}

add_filter('mbp_create_post', 'pgmb_insert_content_img', 10, 4);