Fatal error: PHP error in file /var/www/dgx-forum/wcf/lib/system/event/listener/DonationAddFormCodeListener.class.php (0): Declaration of DonationAddFormCodeListener::save() should be compatible with DonationAddFormAbstractListener::save($timestamp = NULL)

Information:

error message: PHP error in file /var/www/dgx-forum/wcf/lib/system/event/listener/DonationAddFormCodeListener.class.php (0): Declaration of DonationAddFormCodeListener::save() should be compatible with DonationAddFormAbstractListener::save($timestamp = NULL)
error code: 0
file: /var/www/dgx-forum/wcf/lib/system/WCF.class.php (255)
php version: 5.6.40-0+deb8u2
wcf version: 1.0.11 pl 4 (Horizon)
date: Sat, 20 Apr 2019 20:15:26 +0000
request: /index.php?form=DonationAdd&s=203d2d026f3725bf7a02157e6e138af93c82b3b8
referer:

Stacktrace:

#0 /var/www/dgx-forum/wcf/lib/system/event/EventHandler.class.php(175): WCF::handleError(2048, 'Declaration of ...', '/var/www/dgx-fo...', 0, Array)
#1 /var/www/dgx-forum/wcf/lib/system/event/EventHandler.class.php(175): EventHandler::fireAction()
#2 /var/www/dgx-forum/wcf/lib/page/AbstractPage.class.php(55): EventHandler::fireAction(Object(DonationAddForm), 'readData')
#3 /var/www/dgx-forum/wcf/lib/form/AbstractForm.class.php(91): AbstractPage->readData()
#4 /var/www/dgx-forum/wcf/lib/page/AbstractPage.class.php(74): AbstractForm->readData()
#5 /var/www/dgx-forum/wcf/lib/form/DonationAddForm.class.php(48): AbstractPage->show()
#6 /var/www/dgx-forum/wcf/lib/page/AbstractPage.class.php(36): DonationAddForm->show()
#7 /var/www/dgx-forum/wcf/lib/util/RequestHandler.class.php(63): AbstractPage->__construct()
#8 /var/www/dgx-forum/wcf/lib/util/RequestHandler.class.php(94): RequestHandler->__construct('DonationAdd', Array, 'form')
#9 /var/www/dgx-forum/index.php(15): RequestHandler::handle(Array)
#10 {main}