<?php

class A
{
    public function abc()
    {
        $a = '';
        $a .= self::test();
        $a .= static::test();
        return $a;
    }

    public static function test()
    {
        return 'A';
    }

    public function __toString()
    {
        return get_class($this) . "\n";
    }

    public static function createSelfObject()
    {
        return new self();
    }

    public static function createStaticObject()
    {
        return new static();
    }
}

class B extends A
{
    public function abc()
    {
        return parent::abc() . "\n";
    }

    public static function test()
    {
        return 'B';
    }
}

$a = new A();
echo "Class A: ";
echo $a->abc();
echo "***\n";

$b = new B();
echo "Class B: ";
echo $b->abc();
echo "***\n";

$a1 = A::createSelfObject();
echo 'A::createSelfObject() -> ' . $a1;
$a2 = A::createStaticObject();
echo 'A::createStaticObject() -> ' . $a2;
$b1 = B::createSelfObject();
echo 'B::createSelfObject() -> ' . $b1;
$b2 = B::createStaticObject();
echo 'B::createStaticObject() -> ' . $b2;