$ curl -sS https://getcomposer.org/installer | php

2.常用一些操作


composer self-update  //php composer.phar self-update


composer update  -o   //-o, --optimize-autoloader      Optimize autoloader during autoloader dump.


composer update foo/bar  //仅更新单个库

composer require "foo/bar:1.0.0"    //你可能会觉得每安装一个库都需要修改composer.json太麻烦，那么你可以直接使用require命令

3.国内因为XXX原因，下载包会慢，所以可以设置国内镜像

（1）修改 composer 的全局配置文件：config.json

windows打开cmd 执行如下命令或Linux、Mac 执行如下命令：

composer config repo.packagist composer https://packagist.phpcomposer.com

执行命令：

composer config repo.packagist composer https://packagist.phpcomposer.com

"repositories": {
    "packagist": {  
           "type": "composer",  
           "url": "https://packagist.phpcomposer.com"
    } 
}

4.项目下 
 如果执行:composer update 报一下如下错误时： 

Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to allocate 72 bytes) in
phar:///usr/local/Cellar/composer/1.2.4/libexec/composer.phar/src/Composer/DependencyResolver/RuleWatchGraph.php on line 47

执行：php -d memory_limit=2G composer update  //要是执行报：Could not open input file: composer  
 
执行：php -d memory_limit=2G composer.phar update  //要是执行报：Could not open input file: composer.phar  
 
执行：curl -sS https://getcomposer.org/installer | php 
 
然后执行：php -d memory_limit=4G composer.phar update 

ps:内容参考官网http://www.phpcomposer.com，更多具体使用看官方文档