awesome PHP之依赖注入容器pimple
依赖注入（Dependency Injection）又叫控制反转（Inversion of Control）是一个重要的面向对象编程的法则来削减计算机程序的耦合问题，它能消除组件间的直接依赖关系，让组件的开发更独立，使用更灵活，在java框架中应用非常广泛。在php中由于语言特性不能完全照搬java的那一套，但简单的功能还是可以实现的。pimple就是php社区中比较流行的一种ioc容器。

可以用composer添加 require  "pimple/pimple": "1.*"

pimple的优势是简单，就一个文件

<?php

/*
 * This file is part of Pimple.
 *
 * Copyright (c) 2009 Fabien Potencier
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is furnished
 * to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/**
 * Pimple main class.
 *
 * @package pimple
 * @author  Fabien Potencier
 */
class Pimple implements \ArrayAccess
{
    private $values = array();
    private $factories;
    private $protected;
    private $frozen = array();
    private $raw = array();
    private $keys = array();

    /**
     * Instantiate the container.
     *
     * Objects and parameters can be passed as argument to the constructor.
     *
     * @param array $values The parameters or objects.
     */
    public function __construct(array $values = array())
    {
        $this->factories = new \SplObjectStorage();
        $this->protected = new \SplObjectStorage();

        foreach ($values as $key => $value) {
            $this->offsetSet($key, $value);
        }
    }

    /**
     * Sets a parameter or an object.
     *
     * Objects must be defined as Closures.
     *
     * Allowing any PHP callable leads to difficult to debug problems
     * as function names (strings) are callable (creating a function with
     * the same name as an existing parameter would break your container).
     *
     * @param  string           $id    The unique identifier for the parameter or object
     * @param  mixed            $value The value of the parameter or a closure to define an object
     * @throws RuntimeException Prevent override of a frozen service
     */
    public function offsetSet($id, $value)
    {
        if (isset($this->frozen[$id])) {
            throw new \RuntimeException(sprintf('Cannot override frozen service "%s".', $id));
        }

        $this->values[$id] = $value;
        $this->keys[$id] = true;
    }

    /**
     * Gets a parameter or an object.
     *
     * @param string $id The unique identifier for the parameter or object
     *
     * @return mixed The value of the parameter or an object
     *
     * @throws InvalidArgumentException if the identifier is not defined
     */
    public function offsetGet($id)
    {
        if (!isset($this->keys[$id])) {
            throw new \InvalidArgumentException(sprintf('Identifier "%s" is not defined.', $id));
        }

        if (
            isset($this->raw[$id])
            || !is_object($this->values[$id])
            || isset($this->protected[$this->values[$id]])
            || !method_exists($this->values[$id], '__invoke')