Warning - Cannot use a scalar value as an array

Hi,

Went to Piwik today and saw these warnings at the top:

WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(625): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /path/core/DataTable/Row.php(623): Warning - Cannot use a scalar value as an array - Piwik 3.2.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)

The only thing that changed recently is that yesterday we installed the Piwik A/B testing plugin and started a couple of experiments. However, these warnings didn’t appear after installing the plugin or after starting the experiments. They however appeared now, after half a day of running the experiments.

System settings:
4 users
1 segments
2 experiments
5 websites
44 activated plugins
Piwik version: 3.2.0
MySQL version: 5.6.36
PHP version: 5.5.38

Hope this helps to identify the issue.

Thanks.

Are you using a cronjob for archiving, or is that triggered within the browser?

May be also good to know which success metrics you use in your experiment. Eg goals, goals revenue, bounces, etc. By the sounds it may be related to A/B testing, but we haven’t had any such error before. Knowing the success metrics will help to reproduce the issue.

Yes, using a cron job for archiving.

The success metrics used are all the goals defined (about 5 of them, both % conversions and revenue), as well as bounces, average page visits, visit duration.

The warnings actually disappeared all of a sudden, shortly after I posted the report here. Let me know if there is any other information you would like me to provide.

Hi Borislav,

Ok. If you experience again this issue in the future, please let us know and we will continue to investigate. Thanks,