class_inheritance.php

<?php

abstract class A
{
    public function inheritance()
    {
        return self::p();
    }

    public function inheritance2()
    {
        return $this->pA();
    }

    protected function p()
    {
        return "A";
    }

    protected function pA()
    {
        return "A";
    }

    abstract protected function pB();
    abstract protected function pC();
}

abstract class B extends A
{
    public function inheritance()
    {
        return parent::inheritance() . " <- " . self::p();
    }

    public function inheritance2()
    {
        return parent::inheritance2() . " <- " . $this->pB();
    }

    protected function p()
    {
        return "B";
    }

    protected function pB()
    {
        return "B";
    }
}

class C extends B
{
    public function inheritance()
    {
        return parent::inheritance() . " <- " . $this->p();
    }

    public function inheritance2()
    {
        return parent::inheritance2() . " <- " . $this->pC();
    }

    protected function p()
    {
        return "C";
    }

    protected function pC()
    {
        return "C";
    }
}

$c = new C();
echo "Using ´self´: \n";
echo "{$c->inheritance()} \n";

echo "\n";
echo "Using specific methods: \n";
echo "{$c->inheritance2()} \n";