组合模式

<?php
 
// Component接口，定义了叶子和组合对象的共同操作
interface Component
{
    public function operation(): string;
}
 
// 叶子节点，表示组合的最基本单元
class Leaf implements Component
{
    private $name;
 
    public function __construct($name)
    {
        $this->name = $name;
    }
 
    public function operation(): string
    {
        return "Leaf " . $this->name;
    }
}
 
// 组合节点，表示可以包含其他叶子或组合的对象
class Composite implements Component
{
    private $children = [];
 
    public function add(Component $component)
    {
        $this->children[] = $component;
    }
 
    public function remove(Component $component)
    {
        $this->children = array_filter($this->children, function ($child) use ($component) {
            return $child !== $component;
        });
    }
 
    public function operation(): string
    {
        $result = "Composite (";
        foreach ($this->children as $child) {
            $result .= $child->operation() . " ";
        }
        $result = rtrim($result) . ")";
        return $result;
    }
}
 
// 客户端代码可以统一处理组合和叶子对象
function clientCode(Component $component)
{
    echo "RESULT: " . $component->operation() . "\n";
}
 
// 创建叶子对象
$leaf1 = new Leaf("A");
$leaf2 = new Leaf("B");
 
// 创建组合对象
$composite = new Composite();
$composite->add($leaf1);
$composite->add($leaf2);
 
// 创建更大的组合对象
$composite2 = new Composite();
$composite2->add($composite);
$composite2->add(new Leaf("C"));
 
echo "Client: I've got a simple component:\n";
clientCode($leaf1);
 
echo "\nClient: Now I've got a composite tree:\n";
clientCode($composite2);