composer 服务器安装扩展失败（版本太低的 升级过程）

ps : 服务器 配置
Linux VM-0-9-ubuntu 4.4.0-91-generic #114-Ubuntu SMP Tue Aug 8 11:56:56 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

1. 失败经历

安装 easyswoole 的过程当中，发现没法经过 composer 安装

报错信息以下：

ubuntu@VM-0-9-ubuntu:~/demo/easyswoole$ composer require easyswoole/easyswoole=3.x
./composer.json has been created
Loading composer repositories with package information
Updating dependencies (including require-dev)

Installation failed, deleting ./composer.json.

                                                                                           
  [ErrorException]                                                                         
  "continue" targeting switch is equivalent to "break". Did you mean to use "continue 2"?  
                                                                                           

require [--dev] [--prefer-source] [--prefer-dist] [--no-plugins] [--no-progress] [--no-update] [--update-no-dev] [--update-with-dependencies] [--ignore-platform-reqs] [--sort-packages] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--] [<packages>]..

google 一下，没有对应的错误信息。 想着先查看一下 composer 版本

发现 ： composer 版本太低，就顺便升级composer 升级了再说。

ubuntu@VM-0-9-ubuntu:~/demo/easyswoole$ composer -V
Composer version @package_branch_alias_version@ (1.0.0-beta2) 2016-03-27 16:00:34

升级的过程当中发现，升级失败。 老版本的 composer 不能自动升级

ubuntu@VM-0-9-ubuntu:~$ composer self-update

                                         
  [InvalidArgumentException]             
  Command "self-update" is not defined.

看来是 composer 包过低，都没有自动升级的功能

2. 下载新的 composer 包

1. 新增最新的composer

wget https://dl.laravel-china.org/composer.phar -O /usr/local/bin/composer

 sudo chmod a+x /usr/local/bin/composer

而后把脚本 覆盖到原来的 （经过软链）

2. 查看原来的位置

sudo mv /usr/bin/composer /tmp/ 
sudo ln -s /usr/local/bin/composer  /usr/bin/composer

ubuntu@VM-0-9-ubuntu:~$ composer -V
Composer version 1.8.5 2019-04-09 17:46:47

3. 安装

使用 composer 安装项目