<?php
$string = 'http://n...content-available-to-author-only...e.com/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgQ/additional/segments';
$regex = '~^http://.+?/(?P<token>[^/\n\r]+)~';
echo $match["token"];
PD9waHAKJHN0cmluZyA9ICdodHRwOi8vbi4uLmNvbnRlbnQtYXZhaWxhYmxlLXRvLWF1dGhvci1vbmx5Li4uZS5jb20vZXlKaGJHY2lPaUpJVXpJMU5pSXNJblI1Y0NJNklrcFhWQ0o5LmV5SnpkV0lpT2lJeE1qTTBOVFkzT0Rrd0lpd2libUZ0WlNJNklrcHZhRzRnUkc5bElpd2lZV1J0YVc0aU9uUnlkV1Y5LlRKVkE5NU9yTTdFMmNCYWIzMFJNSHJIRGNFZnhqb1laZ2VGT05GaDdIZ1EvYWRkaXRpb25hbC9zZWdtZW50cyc7CiRyZWdleCA9ICd+Xmh0dHA6Ly8uKz8vKD9QPHRva2VuPlteL1xuXHJdKyl+JzsKcHJlZ19tYXRjaCgkcmVnZXgsICRzdHJpbmcsICRtYXRjaCk7CmVjaG8gJG1hdGNoWyJ0b2tlbiJdOwo=