Description:
------------
We have a trait for handling sessions, which includes (abbreviated):

trait SessionOpenCloseTrait {

  protected function open_session($name) {
    session_name($name);
    session_start();
  }

}

Other classes invoke this using __CLASS__ as the $name parameter:

class SecureToken {

  use SessionOpenCloseTrait;

  public function __construct()   {
    $this->open_session(__CLASS__);
  }

}

When namespaced, __CLASS__ contains a backslash (e.g. "Parent\SecureToken").  This has not been a problem until a security upgrade took us from 7.3.19 to 7.3.27.  After the upgrade the SESSION was being written to the server as normal, but no longer accessible on subsequent requests.  *Possibly* due to encoding of the cookie name.

To fix this, we had to remove the '\':

  protected function open_session($name) {
+   $name = str_replace("\\", "", $name);
    session_name($name);
    session_start();
  }