Hey so I am fairly familiar to the youtube api .. I know how to read channels and playlist along with getting any relevant video information I identify as Important I\'m us
Read documentation at Youtube Data Api
$playlistId = 'REPLACE_WITH_YOUR_PLAYLIST_ID_STARTS_WITH_PL';
$resourceId = new Google_Service_YouTube_ResourceId();
$resourceId->setVideoId('REPLACE_WITH_VIDEO_ID_YOU_WANT_TO_ADD');
$resourceId->setKind('youtube#video');
$playlistItemSnippet = new Google_Service_YouTube_PlaylistItemSnippet();
$playlistItemSnippet->setTitle('YOUR_VIDEO_TITLE');
$playlistItemSnippet->setPlaylistId($playlistId);
$playlistItemSnippet->setResourceId($resourceId);
$playlistItem = new Google_Service_YouTube_PlaylistItem();
$playlistItem->setSnippet($playlistItemSnippet);
$playlistItemResponse = $youtube->playlistItems->insert(
'snippet,contentDetails', $playlistItem, array());
Full project is available at my GitHub