decorator.php

<?php

abstract class Tile {

    abstract function getWealthFactor();
}

////////////////////////////////////////////////////////// 
class Plains extends Tile {

    private $wealthfactor = 2;

    function getWealthFactor() {
        return $this->wealthfactor;
    }

}

////// ////////////////////////////////////////////
abstract class TileDecorator extends Tile {

    protected $tile;

    function __construct(Tile $tile) {
        $this->tile = $tile;
    }

}

///////////////////////////////////////////
class DiamondDecorator extends TileDecorator {

    function getWealthFactor() {
        return $this->tile->getWealthFactor() + 2;
    }

}

////////////////////////////////////////////////// 
class PollutionDecorator extends TileDecorator {

    function getWealthFactor() {
        return $this->tile->getWealthFactor() - 4;
    }

}

////////////////////////////////////////////////////////
$tile = new Plains();
print $tile->getWealthFactor(); // 2 
///////////////////////////////////////////////////////
$tile = new DiamondDecorator(new Plains());
print $tile->getWealthFactor(); // 4 
//////////////////////////////////////////////////////////
$tile = new PollutionDecorator(
        new DiamondDecorator(new Plains()));
print $tile->getWealthFactor(); // 0