Broken graph displayed on quiz results page

Turning down priority to trivial.

I thought GD was required to install Moodle?

Its recommended but not required.

Ah, I see, in report/stats there is code like

if (empty($CFG->gdversion)) {
    echo "(".get_string("gdneed").")";
} else {
    // ...
}

I will make a similar change in the quiz reports.

I suppose this GD requirement probably prevents Moodle from being installed on cheap hosts, but I increasingly think we should make it a requirement. (Especially for the 2.3 thumbnail generation)

I have created MDL-34331 for making GD a requirement.

Thanks Tim, this has been integrated now.

Test result: Success!

Tested in 2.2, 2.3 and Master.

With GD off, the graphs were replaced by the same text as the heading above rather than an error message. I suppose that's not critical, but I thought you might want to know. I will attach a screenshot.

That screen grab looks wrong. What you are seeing there is the web browser failing to display the image, and so displaying the alt text instead.

What you should see if the lang string gdneed.

I suspect the reason for this is that the text Moodle uses to see if gd is installed is to check $CFG->gdversion. I guess Moodle works that out on install/upgrade, and then uses the cached value. To really test this, perhaps you need to disable gd, and then delete the gdversion row from the config table?

*Notice*: Undefined variable: friendlyintegrator in /Users/danp/git/tokenintegrationthanks.php on line 26

Congratulations

!

You've made into Moodle

+

I would like to personally thank you for this contribution on behalf of all Moodle users throughout the world.

cheers!

I've updated to the latest 2.3.1 release that contains this fix. I'm still seeing the problem. I'm running PHP 5.4.5 (GD is enabled, of course) and I see the alt text displayed and no image.

If you look at this bug closely you will see that it says Fix version/s: 2.3.2, so it should not come as a surprise that it is still broken in 2.3.1.

The fix was added to MOODLE_23_STABLE 8 days ago:

http://git.moodle.org/gw?p=moodle.git;a=commit;h=8242298e4b962d3d92776a6c96d0f41353a62ccb

The latest weekly update to Moodle 2.3.1 came out 5 days ago, which contains the files modified by this fix:

http://git.moodle.org/gw?p=moodle.git;a=commit;h=04de7affb6f43aaea6f14e1d25ed9872860bb430

I update to the latest weekly each weekend.

In that case you are running a 2.3.1+ build. The distinction is somewhat pedantic, but that sort of precision is important when reporting bugs.

If you have GD, then actually this bug is probably not related to what you are seeing.

Anyway, what you need to do to diagnose this further is:

1. Set http://docs.moodle.org/23/en/Debugging to DEVELOPER level.

2. Go to the quiz reports, right click on the broken image, and do Open in new tab.

3. If that displays error messages on-screen, then copy and paste them to this bug, or to a new bug report, if that seems more relevant.

4. If you get a message about the image being corrupted, then save it to disc, rename it to .txt, open it in a text editor, and copy and paste the error messages.

Sorry, yes, 2.3.1+.

When the report page is visited, the error log displays:

[Tue Jul 24 09:40:47 2012] [error] [client x.x.x.x] Premature end of script headers: overviewgraph.php, referer: http://www.website.com/moodle/mod/quiz/report.php?id=99845&mode=overview

Right clicking on the broken image and viewing the image results in a 500 Internal Server Error on the page:

http://www.website.com/moodle/mod/quiz/report/overview/overviewgraph.php?id=7175

I also just tested on a clean install of Moodle 2.3.1+ and the error still occurs.

Should I file a new bug report?

I am not sure this is a Moodle problem as such. Try googling that error message. E.g. http://htmlfixit.com/cgi-tutes/tutorial_Common_Web_dev_error_messages_and_what_they_mean.php#premature

Also, try some of the other places in Moodle that output graphs, do any of them work?

Yes, the graphs on all of the activity reports work fine. Graphs in the statistic reports also work correctly.

I did some more testing on my test VM and the problem occurs with PHP 5.4.5. I rolled back to PHP 5.3.15 and the graphs display correctly.

After some testing, the problem seems to be with the line in reportlib.php, function quiz_report_grade_bands():

unset($data[$bands]);

There is definitely a PHP 5.4 issue here. I have made a small script to show this issue. I'll submit it to PHP to get this fixed. It has something to do with how $bands or $foo in this case is cast. It starts as a string, then becomes a double, but something is wrong with it because if you cast the variable as anything the unset() statement will work as intended. Event casting it as a double works:

$test = array("5"=>"bar");
$foo = "10.0000"; // gettype($foo) = "string"
$foo /= 2; //Makes $foo = 5 but still gettype($foo) = "double"
echo gettype($foo);
unset($test[$foo]);

However, if Moodle would like to be proactive in this, it could be fixed on your end by casting the variable $bands like so...

unset($data[(int) $bands]);

Excellent analysis. Thank you. Please could someone open a new issue for this.

Tim, are we waiting on a Moodle developer to open a new issue? Or should we go ahead and make a new issue?

This is a critical bug for those running a server on Windows with an Apache/mod_php configuration(the most common). Every time a quiz results page is visited, Apache crashes with a "Parent: child process exited with status 255 – Restarting." error.

Well, someone needs to create the issue. It does not matter who. I was hoping someone else would do it, but actually, I will do it now.

MDL-34589 now created.