You should really redirect before you start page output

line 747 of /lib/outputrenderers.php: call to debugging()

line 2633 of /lib/weblib.php: call to core_renderer->redirect_message()

line 239 of /backup/util/ui/base_ui.class.php: call to redirect()

line 196 of /backup/util/ui/backup_ui_stage.class.php: call to base_ui->cancel_process()

line 110 of /backup/util/ui/base_ui.class.php: call to backup_ui_stage_schema->process()

line 113 of /backup/backup.php: call to base_ui->process()