How to manipulate the data in this object?

I am trying to manipulate some data coming in the object, but being unsuccessful. I have tried $endNotices[0]->hours $endNotices[0]->{"hours"} and much more.

I am mainly trying to extract the 'seriesId' data in the following:

Array
(

[0] => ReminderNotice Object
 (

[seriesId:ReminderNotice:private] => 338

I am trying to grab only the number 338.

Below is the code I am using to write the data to the file:

$endNotices = $repository->GetReminderNotices(Date::Now(), ReservationReminderType::End);
Log::Debug('Found %s end reminders', count($endNotices));
    $my_file = 'file.txt';
    $handle = fopen($my_file, 'w') or die('Cannot open file:  '.$my_file);
    //$data =  print_r($endNotices, true);
    fwrite($handle,  print_r($endNotices[0], true));

foreach ($endNotices as $notice)
{
    ServiceLocator::GetEmailService()->Send(new ReminderEndEmail($notice));

}

The result being printed to the file is:

Array
(

[0] => ReminderNotice Object
 (

[seriesId:ReminderNotice:private] => 338

[reservationId:ReminderNotice:private] => 328

[referenceNumber:ReminderNotice:private] => 5745cc5bbee9b783620114

[startDate:ReminderNotice:private] => Date Object
                (

[date:Date:private] => DateTime Object
                        (

[date] => 2016-05-25 05:00:00

[timezone_type] => 3

[timezone] => UTC
                        )

[parts:Date:private] => Array
                        (

[hours] => 05

[minutes] => 00

[seconds] => 00

[mon] => 05

[mday] => 25

[year] => 2016

[wday] => 3
                        )

[timezone:Date:private] => UTC

[timestring:Date:private] => 2016-05-25 05:00:00

[timestamp:Date:private] => 1464152400
                )


[endDate:ReminderNotice:private] => Date Object
                (

[date:Date:private] => DateTime Object
                        (

[date] => 2016-05-25 19:00:00

[timezone_type] => 3

[timezone] => UTC
                        )


[parts:Date:private] => Array
                        (

[hours] => 19

[minutes] => 00

[seconds] => 00

[mon] => 05

[mday] => 25

[year] => 2016

[wday] => 3
                        )

[timezone:Date:private] => UTC

[timestring:Date:private] => 2016-05-25 19:00:00

[timestamp:Date:private] => 1464202800
                )

[title:ReminderNotice:private] => 

[description:ReminderNotice:private] => 

[resourceName:ReminderNotice:private] => TEST-RESOURCE

[emailAddress:ReminderNotice:private] => dansmith@gmail.com

[firstName:ReminderNotice:private] => Dan

[lastName:ReminderNotice:private] => Smith

[timezone:ReminderNotice:private] => America/Chicago

[reminder_minutes:ReminderNotice:private] => 

[language:ReminderNotice:private] => en_us
        )

)

This is exactly what I want, but printing the variable