php设计模式-简单依赖注入容器的闭包方式实现

<?php
class A 
{
    private $_b;

    public function __construct($b)
    {
        $this->_b = $b;
    }

    public function sayHello()
    {
        $this->_b->sayHello();
        echo 'I am A<br>';
    }
}

class B
{
    private $_c;

    public function __construct($c)
    {
        $this->_c = $c;
    }

    public function sayHello()
    {
        $this->_c->sayHello();
        echo 'I am B<br>';
    }
}

class C
{
    public function sayHello()
    {
        echo 'I am C<br>';
    }
}

// 依赖注入容器
class DIContainer
{
    private $_container;

    public function bind($key, Callable $resolver)
    {
        $this->_container[$key] = $resolver;
    }

    public function make($classname)
    {
        if (!isset($this->_container[$classname])) throw new Exception('unregister class:' . $classname);
        return $this->_container[$classname]($this);
    }
}

$container = new DIContainer();
$container->bind('c', function(){
    return new C;
});

$container->bind('b', function($container){
    return new B($container->make('c'));
});

$container->bind('a', function($container){
    return new A($container->make('b'));
});

$a = $container->make('a');
$a->sayHello();

　　结果:

I am C
I am B
I am A