Using the YouTube API to upload videos to a single channel is straightforward. This is how I currently do it using the PHP Client Library:
<?php
/**
 * This sample adds new tags to a YouTube video by:
 *
 * 1. Retrieving the video resource by calling the "youtube.videos.list" method
 *    and setting the "id" parameter
 * 2. Appending new tags to the video resource's snippet.tags[] list
 * 3. Updating the video resource by calling the youtube.videos.update method.
 *
 * @author Ibrahim Ulukaya
*/
/**
 * Library Requirements
 *
 * 1. Install composer (https://getcomposer.org)
 * 2. On the command line, change to this directory (api-samples/php)
 * 3. Require the google/apiclient library
 *    $ composer require google/apiclient:~2.0
 */
if (!file_exists(__DIR__ . '/vendor/autoload.php')) {
  throw new \Exception('please run "composer require google/apiclient:~2.0" in "' . __DIR__ .'"');
}
require_once __DIR__ . '/vendor/autoload.php';
session_start();
/*
 * You can acquire an OAuth 2.0 client ID and client secret from the
 * {{ Google Cloud Console }} <{{ https://cloud.google.com/console }}>
 * For more information about using OAuth 2.0 to access Google APIs, please see:
 * <https://developers.google.com/youtube/v3/guides/authentication>
 * Please ensure that you have enabled the YouTube Data API for your project.
 */
$OAUTH2_CLIENT_ID = 'REPLACE_ME';
$OAUTH2_CLIENT_SECRET = 'REPLACE_ME';
$client = new Google_Client();
$client->setClientId($OAUTH2_CLIENT_ID);
$client->setClientSecret($OAUTH2_CLIENT_SECRET);
$client->setScopes('https://www.googleapis.com/auth/youtube');
$redirect = filter_var('http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'],
    FILTER_SANITIZE_URL);
$client->setRedirectUri($redirect);
// Define an object that will be used to make all API requests.
$youtube = new Google_Service_YouTube($client);
// Check if an auth token exists for the required scopes
$tokenSessionKey = 'token-' . $client->prepareScopes();
if (isset($_GET['code'])) {
  if (strval($_SESSION['state']) !== strval($_GET['state'])) {
    die('The session state did not match.');
  }
  $client->authenticate($_GET['code']);
  $_SESSION[$tokenSessionKey] = $client->getAccessToken();
  header('Location: ' . $redirect);
}
if (isset($_SESSION[$tokenSessionKey])) {
  $client->setAccessToken($_SESSION[$tokenSessionKey]);
}
// Check to ensure that the access token was successfully acquired.
if ($client->getAccessToken()) {
  $htmlBody = '';
  try{
    // REPLACE this value with the video ID of the video being updated.
    $videoId = "VIDEO_ID";
    // Call the API's videos.list method to retrieve the video resource.
    $listResponse = $youtube->videos->listVideos("snippet",
        array('id' => $videoId));
    // If $listResponse is empty, the specified video was not found.
    if (empty($listResponse)) {
      $htmlBody .= sprintf('<h3>Can\'t find a video with video id: %s</h3>', $videoId);
    } else {
      // Since the request specified a video ID, the response only
      // contains one video resource.
      $video = $listResponse[0];
      $videoSnippet = $video['snippet'];
      $tags = $videoSnippet['tags'];
      // Preserve any tags already associated with the video. If the video does
      // not have any tags, create a new list. Replace the values "tag1" and
      // "tag2" with the new tags you want to associate with the video.
      if (is_null($tags)) {
        $tags = array("tag1", "tag2");
      } else {
        array_push($tags, "tag1", "tag2");
      }
      // Set the tags array for the video snippet
      $videoSnippet['tags'] = $tags;
      // Update the video resource by calling the videos.update() method.
      $updateResponse = $youtube->videos->update("snippet", $video);
      $responseTags = $updateResponse['snippet']['tags'];
      $htmlBody .= "<h3>Video Updated</h3><ul>";
      $htmlBody .= sprintf('<li>Tags "%s" and "%s" added for video %s (%s) </li>',
          array_pop($responseTags), array_pop($responseTags),
          $videoId, $video['snippet']['title']);
      $htmlBody .= '</ul>';
    }
  } catch (Google_Service_Exception $e) {
    $htmlBody .= sprintf('<p>A service error occurred: <code>%s</code></p>',
        htmlspecialchars($e->getMessage()));
  } catch (Google_Exception $e) {
    $htmlBody .= sprintf('<p>An client error occurred: <code>%s</code></p>',
        htmlspecialchars($e->getMessage()));
  }
    $_SESSION[$tokenSessionKey] = $client->getAccessToken();
} elseif ($OAUTH2_CLIENT_ID == 'REPLACE_ME') {
  $htmlBody = <<<END
  <h3>Client Credentials Required</h3>
  <p>
    You need to set <code>\$OAUTH2_CLIENT_ID</code> and
    <code>\$OAUTH2_CLIENT_ID</code> before proceeding.
  <p>
END;
} else {
  // If the user hasn't authorized the app, initiate the OAuth flow
  $state = mt_rand();
  $client->setState($state);
  $_SESSION['state'] = $state;
  $authUrl = $client->createAuthUrl();
  $htmlBody = <<<END
<h3>Authorization Required</h3>
<p>You need to <a href="$authUrl">authorize access</a> before proceeding.<p>
END;
}
?>
<!doctype html>
<html>
<head>
<title>Video Updated</title>
</head>
<body>
  <?=$htmlBody?>
</body>
</html>
update_video.php
The very first time the script runs, I am prompted with a window to authenticate the request, a token is granted and expires in 60 minutes.
I want to use the same script to upload videos to different channels which I own. For example if I have 3 different channels I can sign in to different browsers to authenticate the application. I currently have more than 10 YouTube channels that I want to upload content to after every few hours.
Is there a way I can manage all these channels from a central service so as to avoid authenticating each time I add a new channel. Or is there a way to authenticate the YouTube API using my YouTube login details?
 
     
     
    