failed to open stream auto-load error

[freddy-daniel]

PS C:\xampp-5\htdocs\myoauth> curl -u testclient:testpass http://localhost/myoauth/token.php -d 'grant_type=client_credentials'
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<b>Warning</b>:  require_once(oauth2-server-php/src/OAuth2/Autoloader.php): failed to open stream: No such file or directory in <b>C:\xampp-5\htdocs\myoauth\server.php</b> on line <b>12</b><br />
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<b>Fatal error</b>:  require_once(): Failed opening required 'oauth2-server-php/src/OAuth2/Autoloader.php' (include_path='C:\xampp-5\php\PEAR') in <b>C:\xampp-5\htdocs\myoauth\server.php</b> on line <b>12</b><br />
PS C:\xampp-5\htdocs\myoauth>

This error persisting from 2013 now it's 2018, How to fix it? Is this deprecated library ? This Issue (require autoload.php #18) is closed but problem still exist.