content-strip.php

<?php

function nyo_truncate_content ( $content ) {
	require_once( AMP__DIR__ . '/includes/utils/class-amp-dom-utils.php' );

	$elementsRemaining = 2;
	$contentDOM = \AMP_DOM_Utils::get_dom_from_content(apply_filters('the_content', $content) ); // Returns a DOMDocument
	$contentDOMParsed = clone $contentDOM;

	// Strip all elements from the body.
	$originalBody = $contentDOM->getElementsByTagName('body')->item(0);
	$parsedBody = $contentDOMParsed->getElementsByTagName('body')->item(0);
	while ($parsedBody->hasChildNodes()) {
		// We're starting fresh. Remove all existing elements from the processed clone
		$parsedBody->removeChild($parsedBody->firstChild);
	}

	foreach($originalBody->childNodes as $element) {
		if ($elementsRemaining < 0) { // We are out of the number of elements we want
			break;
		}

		// Import Node into new document and append.
		$importedNode = $contentDOMParsed->importNode($element, true);
		$parsedBody->appendChild($importedNode);
		$elementsRemaining--;
	}

	$content = \AMP_DOM_Utils::get_content_from_dom( $contentDOMParsed ); // Returns ONLY what's within the body tag, in string format.
	return $content;
}