Wordpress Filter - Youtube Video Resize to 16:9 using Bootstrap 3 Embed Responsive

wordpress_youtube_responsive_filter.php

<?php
//
// ADD TO YOUR THEME functions.php
// @author Glauber Portella <glauberportella@gmail.com>
//

/**
 * Resize youtube videos
 * Redim youtube videos URL that exists on content to be embed responsive using Bootstrap 3 embed responsive feature
 * Needs theme with Bootstrap 3 support
 */
function d4w_youtube_responsive_filter($content) {
	$replacement = '<div class="embed-responsive embed-responsive-16by9">$1</div>';
	$regex = '#((<iframe.+?)(class="(.*?)")?(.+?src="https?:\/\/(?:www\.)?(?:youtube.com|youtu.be).*"[^>]+?></iframe>))#i';

	$newContent = preg_replace_callback($regex, function($match) {
		// replace class attr
		$classRegex = '/class="(.*?)"/i';
		$hasClass = preg_match($classRegex, $match[1]);
		if (false !== $hasClass && $hasClass > 0) {
			// class attr exists on iframe
			$newIframe = preg_replace($classRegex, 'class="$1 embed-responsive-item"', $match[1]);
		} else {
			// no class attr exists on iframe
			$replaceRegex = '/^<iframe/i';
			$newIframe = preg_replace($replaceRegex, '<iframe class="embed-responsive-item"', $match[1]);
		}
		return $newIframe;
	}, $content);

	$newContent = preg_replace($regex, $replacement, $newContent);

	return $newContent;
}
add_filter( 'the_content', 'd4w_youtube_responsive_filter' );