ReflectionClass::getParentClass

To find all parents of a class you can use the following code:

        $class = new ReflectionClass('classname');
        
        $parents = [];
        
        while ($parent = $class->getParentClass()) {
            $parents[] = $parent->getName();
            $class = $parent;
        }
        
        echo "Parents: " . implode(", ", $parents);