Why would anybody need to know that? For me it's using it in a sql query in combination with a like request.

The simple solution: Use two of them.

$likeQuery = sprintf('
  SELECT *
  FROM `user` u
  WHERE u.roles LIKE "%%%s%%"
', User::ROLE_ADMIN);

Which will result in:

'SELECT * FROM `user` u WHERE u.roles LIKE "%ROLE_ADMIN%"'