Just upgraded a cacti server to Stretch/Debian 9. Cacti was still working after the upgrade was finished.
After cleaning up the leftover Debian 8 PHP 5 packages, that left only PHP 7.0 installed, cacti stopped working, giving only a blank page when accessing the URL.
/usr/share/cacti/site/index.php from the command line gives the error:
PHP Fatal error: Uncaught Error: Call to undefined function mysql_pconnect() in /usr/share/php/adodb/drivers/adodb-mysql.inc.php:480
What to do to make it work?