Running the archive via cron will result often in errors "Illegal string offset 'XAxisDisplay' 'XAxisFormat' "

[tuxmaster]

Some jobs will run without any error and other will fail.
Piwik: 3.0.0
PHP: 7.1
Here the error:
NFO [2016-12-30 06:50:05] Scheduler: executing task Piwik\Plugins\ScheduledReports\API.sendReport_4...
WARNING [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(73): Warning - Illegal string offset 'XAxisDisplay' - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(74): Warning - Illegal string offset 'XAxisFormat' - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(74): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(75): Warning - Illegal string offset 'XAxisName' - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(75): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(76): Warning - Illegal string offset 'XAxisUnit' - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(76): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(77): Warning - Illegal string offset 'Abscissa' - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(77): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(78): Warning - Illegal string offset 'AbsicssaPosition' - Piwik 3.0.0 - 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 [2016-12-30 06:50:17] /var/www/piwik/libs/pChart/class/pData.class.php(80): Warning - Illegal string offset 'Axis' - Piwik 3.0.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
Uncaught exception: Cannot use string offset as an array
in /var/www/piwik/libs/pChart/class/pData.class.php line 80
#0 /var/www/piwik/plugins/ImageGraph/StaticGraph.php(241): pData->__construct()
#1 /var/www/piwik/plugins/ImageGraph/StaticGraph/GridGraph.php(68): Piwik\Plugins\ImageGraph\StaticGraph->initpData()
#2 /var/www/piwik/plugins/ImageGraph/StaticGraph/Evolution.php(24): Piwik\Plugins\ImageGraph\StaticGraph\GridGraph->initGridChart(true, 691053, false, true, true)
#3 /var/www/piwik/plugins/ImageGraph/API.php(493): Piwik\Plugins\ImageGraph\StaticGraph\Evolution->renderGraph()
#4 [internal function]: Piwik\Plugins\ImageGraph\API->get('2', 'day', '2016-11-30,2016...', 'MultiSites', 'getAll', 'evolution', '2', false, false, true, 700, 200, 9, 11, true, false, false, '222222', 'FFFFFF', 'CCCCCC', false, true, false, false)
#5 /var/www/piwik/core/API/Proxy.php(219): call_user_func_array(Array, Array)
#6 /var/www/piwik/core/API/Request.php(236): Piwik\API\Proxy->call('\Piwik\Plugins\...', 'get', Array)
#7 /var/www/piwik/core/ReportRenderer.php(261): Piwik\API\Request->process()
#8 /var/www/piwik/core/ReportRenderer/Html.php(210): Piwik\ReportRenderer::getStaticGraph(Array, 700, 200, true, NULL)
#9 /var/www/piwik/core/ReportRenderer/Html.php(175): Piwik\ReportRenderer\Html->getAttachment(Array, Array, 'Donnerstag, 29....')
#10 /var/www/piwik/plugins/ScheduledReports/API.php(942): Piwik\ReportRenderer\Html->getAttachments(Array, Array, 'Donnerstag, 29....')
#11 /var/www/piwik/plugins/ScheduledReports/API.php(500): Piwik\Plugins\ScheduledReports\API->getAttachments(Object(Piwik\ReportRenderer\Html), Array, Array, 'Donnerstag, 29....')
#12 /var/www/piwik/plugins/ScheduledReports/API.php(557): Piwik\Plugins\ScheduledReports\API->generateReport('4', '2016-12-29', 'de', 2, 'day')
#13 [internal function]: Piwik\Plugins\ScheduledReports\API->sendReport('4')
#14 /var/www/piwik/core/Scheduler/Scheduler.php(227): call_user_func(Array, '4')
#15 /var/www/piwik/core/Scheduler/Scheduler.php(124): Piwik\Scheduler\Scheduler->executeTask(Object(Piwik\Scheduler\Task))
#16 /var/www/piwik/plugins/CoreAdminHome/API.php(58): Piwik\Scheduler\Scheduler->run()
#17 /var/www/piwik/core/CronArchive.php(536): Piwik\Plugins\CoreAdminHome\API->runScheduledTasks()
#18 /var/www/piwik/core/CronArchive.php(290): Piwik\CronArchive->runScheduledTasks()
#19 /var/www/piwik/core/Access.php(469): Piwik\CronArchive->Piwik{closure}()
#20 /var/www/piwik/core/CronArchive.php(292): Piwik\Access::doAsSuperUser(Object(Closure))
#21 /var/www/piwik/plugins/CoreConsole/Commands/CoreArchiver.php(27): Piwik\CronArchive->main()
#22 /var/www/piwik/vendor/symfony/console/Symfony/Component/Console/Command/Command.php(257): Piwik\Plugins\CoreConsole\Commands\CoreArchiver->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#23 /var/www/piwik/vendor/symfony/console/Symfony/Component/Console/Application.php(874): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#24 /var/www/piwik/vendor/symfony/console/Symfony/Component/Console/Application.php(195): Symfony\Component\Console\Application->doRunCommand(Object(Piwik\Plugins\CoreConsole\Commands\CoreArchiver), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#25 [internal function]: Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#26 /var/www/piwik/core/Console.php(79): call_user_func(Array, Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#27 /var/www/piwik/core/Access.php(469): Piwik\Console->Piwik{closure}()
#28 /var/www/piwik/core/Console.php(80): Piwik\Access::doAsSuperUser(Object(Closure))
#29 /var/www/piwik/vendor/symfony/console/Symfony/Component/Console/Application.php(126): Piwik\Console->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#30 /var/www/piwik/console(27): Symfony\Component\Console\Application->run()
#31 {main}

[mattab]

Reupload all files from Piwik 3 as it looks like some files are not uploaded correctly?

[tuxmaster]

The update was done via the update function of piwik and no error was reported.
So the update function has an problem or the files are correct and the problem comes from anywhere else.

[mattab]

Ok re-opening this issue. Does anyone else experience this error message?

[CarlOrff]

Yes, I get this particular error message even with manual download of PDF reports. And it doesn't depend upon the PHP version (tried 7.1.0, 7.0.14 and 5.5.9).

Piwik encoutered an error: Uncaught Error: Cannot use string offset as an array in /var/www/vhosts/xxxxxxx/piwik/libs/pChart/class/pData.class.php:80 Stack trace: #0 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/StaticGraph.php(241): pData->__construct() #1 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/StaticGraph/GridGraph.php(68): Piwik\Plugins\ImageGraph\StaticGraph->initpData() #2 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/StaticGraph/Evolution.php(24): Piwik\Plugins\ImageGraph\StaticGraph\GridGraph->initGridChart(true, 691053, false, true, true) #3 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/API.php(493): Piwik\Plugins\ImageGraph\StaticGraph\Evolution->renderGraph() #4 [internal function]: Piwik\Plugins\ImageGraph\API->get('1', 'day', 'last30', 'VisitsSummary', 'get', 'evolution', '2', false, false, true, 760, 220, 9, 11, true, false, false, '222222', 'FFFFFF', 'CCCCCC', false (which lead to: Uncaught Error: Cannot use string offset as an array in /var/www/vhosts/xxxxxxx/piwik/libs/pChart/class/pData.class.php:80 Stack trace: #0 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/StaticGraph.php(241): pData->__construct() #1 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/StaticGraph/GridGraph.php(68): Piwik\Plugins\ImageGraph\StaticGraph->initpData() #2 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/StaticGraph/Evolution.php(24): Piwik\Plugins\ImageGraph\StaticGraph\GridGraph->initGridChart(true, 691053, false, true, true) #3 /var/www/vhosts/xxxxxxx/piwik/plugins/ImageGraph/API.php(493): Piwik\Plugins\ImageGraph\StaticGraph\Evolution->renderGraph() #4 [internal function]: Piwik\Plugins\ImageGraph\API->get('1', 'day', 'last30', 'VisitsSummary', 'get', 'evolution', '2', false, false, true, 760, 220, 9, 11, true, false, false, '222222', 'FFFFFF', 'CCCCCC', false)

[ozbarshalom]

Same here.
Using php 7.1, Getting this error when trying to download an html report.
Pdf reports are working.

[Wilkolicious]

Not using piwik, but found this through googling for a similar problem for our project:

From: http://php.net/manual/en/migration71.incompatible.php

The empty index operator is not supported for strings anymore

Applying the empty index operator to a string (e.g. $str[] = $x) throws a fatal error instead of converting silently to array.

PChart is getting relatively old now (hasn't been updated since 2014). You'll need to search for any places in the code where the variable is initialised as a string, then array elements are added.

These (member) variables should be initialised as an array().

It's a fairly big task, and really, pChart needs to be re-written/refined for PHP7.1 .

[senden9]

I also get this messages if i try to generate a mail report:

DEBUG Piwik\Plugin\Manager[2017-01-25 20:30:55] [8c16b] Loaded plugins: CorePluginsAdmin, CoreAdminHome, CoreHome, WebsiteMeasurable, Diagnostics, CoreVisualizations, Proxy, API, ExamplePlugin, Widgetize, Transitions, LanguagesManager, Actions, Dashboard, MultiSites, Referrers, UserLanguage, DevicesDetection, Goals, Ecommerce, SEO, Events, UserCountry, VisitsSummary, VisitFrequency, VisitTime, VisitorInterest, ExampleAPI, RssWidget, Feedback, Monolog, Login, UsersManager, SitesManager, Installation, CoreUpdater, CoreConsole, ScheduledReports, UserCountryMap, Live, CustomVariables, PrivacyManager, ImageGraph, Annotations, MobileMessaging, Overlay, SegmentEditor, Insights, Morpheus, Contents, BulkTracking, Resolution, DevicePlugins, Heartbeat, Intl, Marketplace, ProfessionalServices, UserId, CustomPiwikJs
WARNING ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(73): Warning - Illegal string offset 'XAxisDisplay' - Piwik 3.0.1 - 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 ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(74): Warning - Illegal string offset 'XAxisFormat' - Piwik 3.0.1 - 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 ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(74): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.1 - Please report this message in thePiwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(75): Warning - Illegal string offset 'XAxisName' - Piwik 3.0.1 - 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 ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(75): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.1 - Please report this message in thePiwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(76): Warning - Illegal string offset 'XAxisUnit' - Piwik 3.0.1 - 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 ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(76): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.1 - Please report this message in thePiwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(77): Warning - Illegal string offset 'Abscissa' - Piwik 3.0.1 - 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 ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(77): Warning - Cannot assign an empty string to a string offset - Piwik 3.0.1 - Please report this message in thePiwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(78): Warning - Illegal string offset 'AbsicssaPosition' - Piwik 3.0.1 - 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 ImageGraph[2017-01-25 20:30:55] [8c16b] /var/www/piwik/libs/pChart/class/pData.class.php(80): Warning - Illegal string offset 'Axis' - Piwik 3.0.1 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)

System:

$ php -v
PHP 7.1.1 (cli) (built: Jan 18 2017 18:44:22) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies

[daberlin]

This looks promising: https://github.com/bozhinov/pChart2.0-for-PHP7

[mattab]

Thanks for the link @daberlin - maybe you would like to try use this updated pChart in Piwik? We'd love your help on this one and a pull request 😎

[mattab]

@sgiehl probably this issue is about

• trying the new pChart lib compatible with PHP7: https://github.com/bozhinov/pChart2.0-for-PHP7 and
• also make it compatible php5 (this PR at least should be needed) https://github.com/bozhinov/pChart2.0-for-PHP7/pull/6/files
• contribute back to pChart any other improvements we make
• Use Pchart over composer
• check tests still pass for PHP7 and PHP5 (our tests should cover most use cases for pChart, now that we've enabled tests for email reports w/ graphs)

[mattab]

This will be released in 3.0.3-rc1 due in the next few hours, feedback welcome