[BUG] Metadata values should be of type array, but are string

[beatrycze-volk]

Description

The value passed to the foreach loop is a string, but should be an array.

Reproduction

Steps to reproduce the behaviour:

1. Install TYPO3 11.x with PHP 8.x
   Click on link to display document page e.g. https://dfgviewer-dist.ddev.site
   See error

Expected Behavior

The values should be stored as arrays or their usage should be adjusted to handle the strings. But the first option is more advisable as imploding and next exploding the array looks like not the most appropriate approach.

Screenshots and Examples

Environment

• RDBMS version: MariaDB 10.3
• TYPO3 version: 11.5.37
• PHP version: 8.2

Additional Context

This line introduces value type change:

    $metadata[$i][$name] = is_array($value)
        ? implode($this->settings['separator'], $value)
        : $value;

But usages of those values are not adjusted e.g:

    foreach ($metadata[$i][$name] as &$langValue) {
        $langValue = Helper::getLanguageName($langValue);
    }

[sebastian-meyer]

There is a preliminary fix in #1339, but this only fixes non-hierarchical metadata. See this for details:

kitodo-presentation/Classes/Controller/MetadataController.php

Lines 172 to 179 in 5240b16

	// PHPStan error
	// I don't understand what this code does, so I take it away until author can fix it
	/*if ($metadata[$i][$name][0] === 'Array') {
	$metadata[$i][$name] = [];
	foreach ($value as $subKey => $subValue) {
	$metadata[$i][$name][$subKey] = $subValue;
	}
	}*/