Return the proper iframe URL for any YouTube, Vimeo, or SoundCloud URL. $cache is a PhpFastCache instance (but not required).

get_embed_url.php

function get_embed_url($url) {
	global $cache;

	// Check for YouTube
	$matchFound = preg_match('/^(https?:\/\/(www\.)?youtube\.com\/watch\?(t=(.+)&)?v=|https?:\/\/youtu\.be\/)([^?]+)(\?(t=(.+))?.*)?$/', $url, $matches);
	if ($matchFound) {
		// Video is a Youtube video
		$url = '//www.youtube.com/embed/' . $matches[5];
		if ($matches[4]) {
			$url = $url . '?start=' . $matches[4];
		} else if ($matches[8]) {
			$url = $url . '?start=' . $matches[8];
		}
	} else {
		// Check for Vimeo
		$matchFound = preg_match('#^https?://vimeo\.com/([a-zA-Z0-9]+)/?$#', $url, $matches);
		if ($matchFound) {
			// Video is a Vimeo video
			$url = '//player.vimeo.com/video/' . $matches[1] . '?byline=0&portrait=0';
		} else if (substr($url, 0, 23) == 'https://soundcloud.com/') {
			// Soundcloud
			$cacheKey = 'oembed-' . md5($url);
			if ($cache) {
				$oembedData = $cache->get($cacheKey);
			} else {
				$oembedData = null;
			}
			if (!$oembedData) {
				$oembedData = file_get_contents('https://soundcloud.com/oembed?format=json&url=' . urlencode($url));
				if ($oembedData) {
					$oembedData = json_decode($oembedData);
					if (is_object($oembedData) && $cache) {
						$cache->set($cacheKey, $oembedData);
					}
				}
			}
			if (is_object($oembedData) && $oembedData->html) {
				$matchFound = preg_match('/src="(.+?)"/', $oembedData->html, $matches);
				if ($matchFound) {
					return $matches[1];
				}
			}
		}
	}
	return $url;
}