functions.php

<?php

// Convert Movie URL
function getMovieUrl($movieUrl)
{
    // Convert YouTube Url
    if (
        strpos($movieUrl, 'youtu.be') !== false ||
        strpos($movieUrl, 'youtube.com/watch') !== false
    ) {
        $movieId = str_replace(array('https://youtu.be/', 'https://www.youtube.com/watch?v=', 'https://www.youtube.com/watch/'), '', $movieUrl);
        return 'https://www.youtube.com/embed/' . $movieId;
    }

    return $movieUrl;
}