Add game-of-life exercice

[resu-xuniL]

Another exercice for validation.

[mk-mxp]

Great contribution. Thanks!

[mk-mxp]

Let's make this a 4. It's looping over a nested array with basic operations and some state tracking.

[mk-mxp]

Once again, I would want another interface: the Game of Life is a state changing exercise using ticks to modify some world state. That's what objects are for. So please make it a class.

To add some "extra spice", suggest to the student in a comment to use Asymmetric Property Visibility. The example.php cannot use this, as it has to support PHP8.2, too.

So the interface may look like this (with the usual exceptions):

class GameOfLife
{
    /**
     * In PHP 8.4 and newer you can use Asymmetric Property Visibility to enhance data encapsulation
     * @see https://www.php.net/manual/en/language.oop5.visibility.php#language.oop5.visibility-members-aviz
     */
    public function __construct(public array $matrix);
    public function tick(): void;
}

And the tests could look like:

        $matrix = [
            [0, 0, 0],
            [0, 1, 0],
            [0, 0, 0]
        ];
        $expected = [
            [0, 0, 0],
            [0, 0, 0],
            [0, 0, 0]
        ];
        $subject = new GameOfLife($matrix);

        $subject->tick();

        $this->assertEquals($expected, $subject->matrix);