This is an OOP version of: http://php.net/manual/de/book.imap.php#96414
To connect to your mailbox instantiate the POP3_Access class with a minimum of these parameters:
use Kreativrudel\Email\POP3_Access;
$pop3 = new POP3_Access( 'mail.example.com', 110, 'username', 'password' );
$pop3->pop3_stat();
$pop3->pop3_list();
$pop3->pop3_retrieve( $msg_id );
$pop3->get_body( $msg_id );