PHP 8.0 changes to count() seem to break questionnaire_check_page_breaks() funtion (Version 3.11.2 (Build - 2023030700))

[NJahreis]

Hi all,

the changes of the behaviour of the count function in PHP 8 seem to cause issues in the questionnaire_check_page_breaks() function in some cases.

I get the following error in my case thenever editing any existing instance of mod_questionnaire with PHP8:

Got error 'PHP message: PHP Warning: Undefined array key 73 in MYPATH/mod/questionnaire/locallib.php on line 756
PHP message: PHP Warning: Trying to access array offset on value of type null in MYPATH/mod/questionnaire/locallib.php on line 758
PHP message: PHP Warning: Trying to access array offset on value of type null in MYPATH/mod/questionnaire/locallib.php on line 785
PHP message: PHP Warning: Undefined array key 72 in MYPATH/mod/questionnaire/locallib.php on line 788
PHP message: PHP Warning: Trying to access array offset on value of type null in MYPATH/mod/questionnaire/locallib.php on line 788
PHP message: PHP Warning: Undefined array key 72 in MYPATH/mod/questionnaire/locallib.php on line 789
PHP message: PHP Warning: Trying to access array offset on value of type null in MYPATH/mod/questionnaire/locallib.php on line 789
PHP message: PHP Warning: Trying to access array offset on value of type null in MYPATH/mod/questionnaire/locallib.php on line 791
PHP message: Default exception handler: Fehler: count(): Argument #1 ($value) must be of type Countable|array, null given Debug: \nError code: generalexceptionmessage\n* line 791 of /mod/questionnaire/locallib.php: TypeError thrown\n* line 288 of /mod/questionnaire/questions.php: call to questionnaire_check_page_breaks()\n', referer: https://MYMOODLE/mod/questionnaire/questions.php

The code in question can be found here:

moodle-mod_questionnaire/locallib.php

Lines 784 to 807 in 47d48c9

	// Add pagebreak between question child and not dependent question that follows.
	if ($qu['type_id'] != QUESPAGEBREAK) {
	$j = $i - 1;
	if ($j != 0) {
	$prevtypeid = $positions[$j]['type_id'];
	$prevdependencies = $positions[$j]['dependencies'];
	$outerdependencies = count($qu['dependencies']) >= count($prevdependencies) ?
	$qu['dependencies'] : $prevdependencies;
	$innerdependencies = count($qu['dependencies']) < count($prevdependencies) ?
	$qu['dependencies'] : $prevdependencies;
	foreach ($outerdependencies as $okey => $outerdependency) {
	foreach ($innerdependencies as $ikey => $innerdependency) {
	if ($outerdependency->dependquestionid === $innerdependency->dependquestionid &&
	$outerdependency->dependchoiceid === $innerdependency->dependchoiceid &&
	$outerdependency->dependlogic === $innerdependency->dependlogic) {
	unset($outerdependencies[$okey]);
	unset($innerdependencies[$ikey]);
	}
	}
	}
	$diffdependencies = count($outerdependencies) + count($innerdependencies);

For testing I changed it so it emulates the old behaviour of the count() function:

        // Add pagebreak between question child and not dependent question that follows.
        if ($qu['type_id'] != QUESPAGEBREAK) {
            $j = $i - 1;
            if ($j != 0) {
                $prevtypeid = $positions[$j]['type_id'];
                $prevdependencies = $positions[$j]['dependencies'];


                $qudepcount = $qu['dependencies'] == null ? 0 : count($qu['dependencies']);
                $prevdepcount = $prevdependencies == null ? 0 : count($prevdependencies);


                $outerdependencies =  $qudepcount >= $prevdepcount ?
                    $qu['dependencies'] : $prevdependencies;
                $innerdependencies =  $qudepcount < $prevdepcount ?
                    $qu['dependencies'] : $prevdependencies;

                foreach ($outerdependencies as $okey => $outerdependency) {
                    foreach ($innerdependencies as $ikey => $innerdependency) {
                        if ($outerdependency->dependquestionid === $innerdependency->dependquestionid &&
                            $outerdependency->dependchoiceid === $innerdependency->dependchoiceid &&
                            $outerdependency->dependlogic === $innerdependency->dependlogic) {
                            unset($outerdependencies[$okey]);
                            unset($innerdependencies[$ikey]);
                        }
                    }
                }


                $outerdepcount = $outerdependencies == null ? 0 : count($outerdependencies);
                $innerdepcount = $innerdependencies == null ? 0 : count($innerdependencies);

                $diffdependencies = $outerdepcount + $innerdepcount;

This seems to resolve the issue but is not a very pretty solution to the problem and I am not sure if it acually fixes the underlying problem or just works around it.

Edit: I have just noticed that the function code has changed in the MOODLE_400_STABLE branch. Maybe the changes just need to be applied to the MOODLE_311_STABLE branch to resolve the issue?

[mchurchward]

This should work in the MOODLE_400_STABLE branch.
I have cherry-picked the fixes from there into a 3.11 branch (Pull request #484). If you can test that, we can merge it in.