gistfile1.php

<?php
abstract class A {
    protected function isCacheable($object) {
        if (!is_object($object) || !($object instanceof CacheableInterface)) {
            return false;
        }

        return true;
    }

    public function store($object) {
        if (!$this->isCacheable($object)) {
            return false;
        }

        $this->storeObject($object);
    }

    abstract protected function storeObject($object);
}

class B extends A {
    protected function storeObject($object) {
        // Do something else
    }
}

class C extends A {
    protected function storeObject($object) {
        // Do something else
    }
}