Pimcore\Model\Document\Hardlink\Wrapper::getProperties PHP Method

    public function getProperties()
    {
        if ($this->properties == null) {
            if ($this->getHardLinkSource()->getPropertiesFromSource()) {
                $sourceProperties = $this->getDao()->getProperties();
            } else {
                $sourceProperties = [];
            }
            if ($this->getSourceDocument()) {
                // if we have a source document, that means that this document is not directly linked, it's a
                // child of a hardlink that uses "childFromSource", so in this case we use the source properties
                // this is especially important for the navigation, otherwise all children will have the same
                // navigation_name as the source hardlink, which doesn't make sense at all
                $sourceProperties = $this->getSourceDocument()->getProperties();
            }
            $hardLinkProperties = [];
            $hardLinkSourceProperties = $this->getHardLinkSource()->getProperties();
            foreach ($hardLinkSourceProperties as $key => $prop) {
                $prop = clone $prop;
                $prop->setInherited(true);
                // if the property doesn't exist in the source-properties just add it
                if (!array_key_exists($key, $sourceProperties)) {
                    $hardLinkProperties[$key] = $prop;
                } else {
                    // if the property does exist in the source properties but it is inherited, then overwrite it with the hardlink property
                    if ($sourceProperties[$key]->isInherited()) {
                        $hardLinkProperties[$key] = $prop;
                    }
                }
            }
            $properties = array_merge($sourceProperties, $hardLinkProperties);
            $this->setProperties($properties);
        }
        return $this->properties;
    }