PHPRunner 6.1 & php 7

Hi all,
Time ago I wrote a simple application with PHPRunner6.1 and SQLite, everything went ok.
Now my server uses Ubuntu 16.04 and php7 (downgrading php is not possible).
The login works, the menu works, too, but when I should have the list of records I get the error "Declaration of ListPage_Simple::buildSearchPanel($xtVarName) should be compatible with ListPage::buildSearchPanel()"
I tried to make the variable error_reporting less restrictive (and restarted Apache), but it hasn't changed anything.
Does anybody have any idea?
Thanks