Building a theme with Boostrap 4 and WordPress 5.0.1. Under Bootstrap's documentation for embed video the following format is required for responsive videos:

<div class="embed-responsive embed-responsive-16by9">
  <iframe class="embed-responsive-item" src="https://www.youtube.com/embed/zpOULjyy-n8?rel=0" allowfullscreen></iframe>

Searching under the tag and reading the following Q&As:

Using wp-test with my function of:

function oembed_mod($cache,$url,$attr,$post_ID) {
    if (stripos($cache,'youtube.com') !== FALSE && stripos($cache,'iframe') !== FALSE) {
        $cache = str_replace('<iframe','<iframe class="embed-responsive-item" ', $cache);
    $classes = [];

    // Add these classes to all embeds.
    $classes_all = array(

    // Check for different providers and add appropriate classes.
    if (false !== strpos($url,'vimeo.com')) {
        $classes[] = 'vimeo-video';

    if (false !== strpos($url,'youtube.com')) {
        $classes[] = 'youtube-video';

    $classes = array_merge($classes,$classes_all);

    return '<div class="' . esc_attr(implode($classes,' ')) . '">' . $cache . '</div>';

I can modify Youtube and Vimeo videos and I get:

<div class="youtube-video embed-responsive embed-responsive-16by9">
    <iframe class="embed-responsive-item"  width="500" height="281" src="https://www.youtube.com/embed/nwe-H6l4beM?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen>

but on my Twitter post testing I get:

<div class="embed-responsive embed-responsive-16by9">
    <blockquote class="twitter-tweet" data-width="500" data-dnt="true">
        <p lang="en" dir="ltr">Doing what you “know” locks you in a prison of the past. Uncertainty is the path to an innovative future.</p>
        <p>&mdash; Carl Smith (@carlsmith) <a href="https://twitter.com/carlsmith/status/258214236126322689?ref_src=twsrc%5Etfw">October 16, 2012</a></p>
    <p><script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>

Is the Twitter feed apart of the oembed? Is there a preferred approach to video only manipulation so that I can ignore Twitter feeds or do I need to write a conditional on the variable $cache if twitter-tweet exists?


I can get my function to work with:

if (stripos($cache,'twitter.com') !== false) :
    return $cache;

but I think my end goal is to know if there is a better/elegant way to go about this. Current setup seems to be somewhat a hack and as already mentioned this doesn't address all youtube URLs unless I code a foreach look for the needle.

1 Answer 1


You should be doing some sort of check at the beginning of your function to ensure you're in an oembed that you actually want to mod. something like

if (strpos($url, youtube.com) === false && strpos($url, vimeo.com) === false) {
    return $cache;

Although you might want to elaborate on that to catch shortened urls like youtu.be as well.

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