I threw this function:

  protected function get_passphrase_list() {

    // 2023-03-30 jj5 - we cache the generated passphrase list in a static variable so we don't
    // have to constantly regenerate it and because we don't want to put this sensitive data
    // into an instance field. If you don't want the passphrase list stored in a static variable
    // override this method and implement differently.

    static $result = null;

    if ( $result !== null ) { return $result; }

    $secret_list = $this->get_config_secret_list();
    $result = [];

    foreach ( $secret_list as $secret ) {

      $result[] = $this->calc_passphrase( $secret );

    }

    return $result;

  }

into ChatGPT and it said:

This is a protected function that returns a list of passphrases based on a list of secret values obtained from another function, get_config_secret_list(). The passphrases are generated using a method called calc_passphrase().

The function checks if the passphrase list has already been generated by looking at a static variable named $result. If $result is not null, the function returns it. Otherwise, the function generates the passphrase list and stores it in the $result variable.

The reason for caching the passphrase list in a static variable is to avoid having to regenerate it every time the function is called, which can be time-consuming. Additionally, it is considered a security best practice not to store sensitive data, such as passphrases, in instance fields.

If you want to change the way the passphrase list is stored, you can override this method and implement it differently.