### Composer
Composer是PHP中用来管理程序包的工具。（后端库管理工具）
官方网站 https://getcomposer.org/
浏览全部程序包 https://packagist.org/
比如 https://packagist.org/packages/yiisoft/yii2-app-advanced
~~~
composer create-project --prefer-dist yiisoft/yii2-app-advanced advanced
~~~
对照composer.json
~~~
"require": {
"php": ">=5.4.0",
"yiisoft/yii2": ">=2.0.6",
"yiisoft/yii2-bootstrap": "*",
"yiisoft/yii2-swiftmailer": "*"
},
"require-dev": {
"yiisoft/yii2-codeception": "*",
"yiisoft/yii2-debug": "*",
"yiisoft/yii2-gii": "*",
"yiisoft/yii2-faker": "*"
}
~~~
### 安装示例
一个有关DateTime的库 https://packagist.org/packages/nesbot/carbon
~~~
composer require nesbot/carbon
# 卸载
composer remove nesbot/carbon
~~~
安装后注意vendor目录和composer.json文件的变化
frontend\controllers\SiteController.php
~~~
use Carbon\Carbon;
public function actionAbout()
{
$myTime = Carbon::now()->addDay(-2)->toDateTimeString();
return $this->render('about', ['model' => $model, 'myTime' => $myTime]);
}
~~~
frontend\views\site\about.php
~~~
/* @var $myTime string */
<p>我的时间：<?= $myTime ?></p>
~~~
### 框架和库
什么是框架（Framework）？
什么是库（Library）？
