Interesting inheritance details in PHP5

[Berislav Lopac]

Consider this code:

<?php
class TestClass
{
private function TestMethod()
{
echo 1;
}

public function TestMe()
{
$this->TestMethod();
}
}

class ExtendedTestClass extends TestClass
{
private function TestMethod()
{
echo 2;
}

}

$test1 = new TestClass();
$test2 = new ExtendedTestClass();

$test1->TestMe();
$test2->TestMe();

?>

Guess what be the output of this code?

I was testing the compliance of PHP5 to the Open-Closed principle, and found
out this strange behavior. In other words, you can override a private
function in a subclass, but if the calling method is declared only in the
superclass and not overriden in subclass, it will still call the original,
superclass's method, instead of the subclass's... Very strange -- or am I
missing something?

berislav

[chernyshevsky]

A situation where you need to use "final," perhaps?

[Berislav Lopac]

ch***********@hotmail.com wrote:

A situation where you need to use "final," perhaps?

Why? The idea is that PHP5 should either comply with the OCP (ie, allow
private methods to be overriden, but not accessed), or not (not allow
private methods to be neither overriden nor accessed). It however won't
complain if you override it, but when you call it from another method it
will depend on where the caller method is defined which method (original or
overriden to call). AFAIK, this is contrary to all the OOP principles I
know...

Berislav

[chernyshevsky]

It follows the ISC principle--implement something on the cheap.