$re = '/(?:(?:www\.facebook\.com\/(?:(?:(?:video\.php)|(?:watch\/))\?v=\d+|(?:[0-9a-zA-Z-_.]+\/(?:(?:video|(post))(?:s))\/)(?:\d+|(?:\w+\.\d+\/)\d+)))|(?:fb\.watch\/(?:\w|-)+)\/?)/m';
$str = 'https://fb.watch/2xoYhkRbF255
https://fb.watch/2xoYhkRbF2/
https://fb.watch/2xo-_v7K6Vj/
https://www.facebook.com/myntpc/videos/842675369629973
https://www.facebook.com/michelle.huang.108889/posts/10157993447446172
https://www.facebook.com/nikololok/videos/t.100000216422619/10153335471682286/?type=2
https://www.facebook.com/something/videos/vb.100001360760001/1371428966245002/?type=2&video_source=user_video_tab
https://www.facebook.com/video.php?v=250367532879495
https://www.facebook.com/watch/?v=250367532879495
<iframe src="https://www.facebook.com/plugins/post.php?href=https://fb.watch/2xoYhkRbF2/&width=500&show_text=true&appId=290536511140551&height=526"width="500"height="526"style="border:none;overflow:hidden"scrolling="no"frameborder="0"allowfullscreen="true"allow="autoplay;clipboard-write;encrypted-media;picture-in-picture;web-share"></iframe>
<iframesrc="https://www.facebook.com/plugins/post.php?href=https://www.facebook.com/michelle.huang.108889/posts/10157993447446172&width=500&show_text=true&appId=290536511140551&height=204"width="500"height="204"style="border:none;overflow:hidden"scrolling="no"frameborder="0"allowfullscreen="true"allow="autoplay;clipboard-write;encrypted-media;picture-in-picture;web-share"></iframe>
<div class="fb-post" data-href="https://www.facebook.com/DailyMailVideo/posts/3729983233749236" data-width="500" data-show-text="true"><blockquote cite="https://www.facebook.com/DailyMailVideo/posts/3729983233749236" class="fb-xfbml-parse-ignore"><p>A new set of eleph-antlers!</p>由 <a href="https://www.facebook.com/DailyMailVideo/">Daily Mail Video</a> 發佈於 <a href="https://www.facebook.com/DailyMailVideo/posts/3729983233749236">2021年1月5日 星期二</a></blockquote></div>
<iframesrc="https://www.facebook.com/plugins/video.php?height=316&href=https://www.facebook.com/1243823171/videos/10217863771006297/&show_text=false&width=560"width="560"height="316"style="border:none;overflow:hidden"scrolling="no"frameborder="0"allowfullscreen="true"allow="autoplay;clipboard-write;encrypted-media;picture-in-picture;web-share"allowFullScreen="true"></iframe>
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php