.youtube-video-container {
  position: relative;
  overflow: hidden;
  width: 100%;
}

.youtube-video-container::after {
  display: block;
  content: "";
  padding-top: 56.25%;
}

.youtube-video-container iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}
Code language: PHP (php)