Add oEmbed support to ACF WYSIWYG fields (acf_the_content)

functions.php

<?php

/**
 * Add oEmbed support to ACF WYSIWYG fields.
 *
 * Fixes issue with WP-native oEmbeds not working in ACF WYSIWYG fields because
 * these fields are saved in the database without post IDs. WP's oEmbed works out
 * of the box only with direct post content.
 */

add_filter('acf_the_content', 'add_oembed');

function add_oembed($content) {
  preg_match_all('/^https?:\/\/.[^\s]+$/m', $content, $matches);

  if ($matches && $matches[0]) {
    $embedCode = '<div class="embed">' . wp_oembed_get($matches[0][0]) . '</div>';

    $content = str_replace($matches[0][0], $embedCode, $content);
  }

  return $content;
}