[v4.0-r1] [Moodle 4.1] [PHP 8.1] htmlspecialchars called with NULL value as first parameter

[danowar2k]

Message from our error logs:

Deprecated: htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated in blocks/onlinesurvey/locallib.php on line 800

Code in question:

    foreach ($parameter as $key => $value) {
        $key = htmlspecialchars($key);
        $value = htmlspecialchars($value);
        if ( $key != "ext_submit" ) {
            $fields[$key] = urlencode($value);
        }
    }

The value line. So there can be parameters with NULL value. Don't know if that's intended, but one should probably check for null values there and don't call this when it's NULL.

[danowar2k]

Maybe the problem isn't at this spot, maybe it is somewhere else where the NULL value is stored to the parameter array. Or even at the spot where the NULL value is stored in the database, don't know yet about the inner workings here.

[danowar2k]

The key that produces this value is resource_link_id.

[danowar2k]

resource_link_id null because of this:

    if (!isset($config->id)) {
        $config->id = null;
    }
    $requestparams = $allparams;
    $requestparams = array_merge($requestparams, lti_build_standard_message($config, $orgid, false));

Because $instance->id in lti_build_standard_message() is $config outside.

[danowar2k]

Final guesswork: config->id is never set because the config_plugins table doesn't have a value for that.

To build the standard LTI request, $instance->id is explicitly required to be present, but not to be set. So you set id to NULL.

So basically, it seems you just have to check for NULL like I said above.