PHP桥接模式Bridge Pattern的优点与实现过程

<?php
// 实现类接口
interface Implementor
{
    public function operationImpl();
}
// 具体实现类A
class ConcreteImplementorA implements Implementor
{
    public function operationImpl()
    {
        return "ConcreteImplementorA operation.";
    }
}
// 具体实现类B
class ConcreteImplementorB implements Implementor
{
    public function operationImpl()
    {
        return "ConcreteImplementorB operation.";
    }
}
// 抽象类
abstract class Abstraction
{
    protected $implementor;
    public function __construct(Implementor $implementor)
    {
        $this->implementor = $implementor;
    }
    abstract public function operation();
}
// 扩展抽象类
class RefinedAbstraction extends Abstraction
{
    public function operation()
    {
        return $this->implementor->operationImpl();
    }
}
// 客户端代码
$implementorA = new ConcreteImplementorA();
$abstraction = new RefinedAbstraction($implementorA);
echo $abstraction->operation(); // 输出 "ConcreteImplementorA operation."

<?php
$implementorA = new ConcreteImplementorA();
$abstraction = new RefinedAbstraction($implementorA);
echo $abstraction->operation(); // 输出 "ConcreteImplementorA operation."