代理模式

<?php

/**
 * 和装饰器模式的区别：装饰器模式为了增强功能，而代理模式是为了加以控制
 *
 * 装饰器为对象添加一个或多个功能，而代理则控制对对象的访问
 */

interface image
{
    public function display();
}

class RealImage implements image
{
    private $_imgSrc;

    public function __construct($imgSrc)
    {
        $this->_imgSrc = $imgSrc;
        $this->loadFromDisk();
    }

    private function loadFromDisk()
    {
        echo "Load {$this->_imgSrc} from disk<br/>";
    }

    public function display()
    {
        echo "Display {$this->_imgSrc}";
    }
}


class ProxyImage implements image
{
    private $_imgSrc;
    private $_realImage;

    public function __construct($imgSrc)
    {
        $this->_imgSrc = $imgSrc;
    }

    public function display()
    {
        if (!$this->_realImage instanceof RealImage) {
            $this->_realImage = new RealImage($this->_imgSrc);
        }

        $this->_realImage->display();
    }
}



$p = new ProxyImage('a.png');
$p->display();

echo "<br/><br/>";
$p->display();