I have (had) a working installation 1.9.12 installation that I had extensively customized, so I'd rather not just reinstall.  What triggered the error was upgrading my server from Ubuntu 14.04 LTS to 16.04 LTS.  This included an upgrade to php7.  After the upgrade my other sites (a Wordpress and a Limesurvey installation) work just fine, but all the pages in my osticket installation come back blank.  I'm showing the following PHP errors in my apache error log: PHP Warning:  Declaration of TicketModel:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.user.php on line 36 PHP Warning:  Declaration of User:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.user.php on line 161 PHP Warning:  Declaration of Organization:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.organization.php on line 0 PHP Warning:  Declaration of DynamicForm:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.dynamic_forms.php on line 0 PHP Warning:  Declaration of DynamicFormField:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.dynamic_forms.php on line 0 PHP Warning:  Declaration of DynamicFormField:() should be compatible with VerySimpleModel:($refetch = false) in /var/www/support/include/class.dynamic_forms.php on line 0 PHP Warning:  Declaration of DynamicFormEntry:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.dynamic_forms.php on line 0 PHP Warning:  Declaration of DynamicFormEntryAnswer:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.dynamic_forms.php on line 0 PHP Warning:  Declaration of SelectionField:() should be compatible with FormField:($widgetClass = false) in /var/www/support/include/class.dynamic_forms.php on line 0 PHP Warning:  Declaration of TypeaheadSelectionWidget:($how) should be compatible with ChoicesWidget:($mode = false) in /var/www/support/include/class.dynamic_forms.php on line 0 PHP Warning:  Declaration of DynamicList:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.list.php on line 132 PHP Warning:  Declaration of DynamicListItem:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.list.php on line 456 PHP Warning:  Declaration of TicketStatus:() should be compatible with VerySimpleModel:($pk = false) in /var/www/support/include/class.list.php on line 779 PHP Warning:  Declaration of TicketStatus:($ht) should be compatible with VerySimpleModel:($ht = false) in /var/www/support/include/class.list.php on line 779 PHP Warning:  Declaration of RandomSequence:() should be compatible with VerySimpleModel:($refetch = false) in /var/www/support/include/class.sequence.php on line 0 PHP Fatal error:  Cannot declare class Error, because the name is already in use in /var/www/support/include/class.error.php on line 0