src/MaterializedPathBehavior.php
public function getParentKey()
    {
        if ($this->owner->isRoot()) {
            return null;
        }
        $path = $this->getPath();
        return array_pop($path);
    }
public function getParentKey()
    {
        if ($this->owner->isRoot()) {
            return null;
        }
        $path = $this->getPath();
        return array_pop($path);
    }
public function getParentKey ( ) { if ( $ this -> owner -> isRoot ( ) ) { return null ; } $ path = $ this -> getPath ( ) ; return array_pop ( $ path ) ; }
Returns key of parent.

@return mixed|null
Returns key of parent .