ubuntu安装composer

1.下载composer.phar

wget https://getcomposer.org/composer.phar

2.重命名composer.phar为composer

mv composer.phar composer

3.增加可执行权限

chmod +x composer

4.现在可以通过./composer 命令运行composer，但这只仅限于在当前目录运行。要想全局使用，composer ，要设置把它为全局变量。找到composer文件，把它移到/usl/local/bin 目录，这样就可以在全局使用composer 命令。

sudo mv composer /usr/local/bin 

5.测试

jiqing@ubuntu:/opt$ composer
   ______
  / ____/___  ____ ___  ____  ____  ________  _____
 / /   / __ \/ __ `__ \/ __ \/ __ \/ ___/ _ \/ ___/
/ /___/ /_/ / / / / / / /_/ / /_/ (__  )  __/ /
\____/\____/_/ /_/ /_/ .___/\____/____/\___/_/
                    /_/
Composer version 1.7-dev (c2fbbe3b86788eb507a0f4f45f9fdc623ca579c4) 2018-03-29 21:36:46

Usage:
  command [options] [arguments]

Options:
  -h, --help                     Display this help message
  -q, --quiet                    Do not output any message
  -V, --version                  Display this application version
      --ansi                     Force ANSI output
      --no-ansi                  Disable ANSI output
  -n, --no-interaction           Do not ask any interactive question
      --profile                  Display timing and memory usage information
      --no-plugins               Whether to disable plugins.
  -d, --working-dir=WORKING-DIR  If specified, use the given directory as working directory.
  -v|vv|vvv, --verbose           Increase the verbosity of messages: 1 for normal output, 2 for more verbose output and 3 for debug

Available commands:
  about                Shows the short information about Composer.
  archive              Creates an archive of this composer package.
  browse               Opens the package's repository URL or homepage in your browser.
  check-platform-reqs  Check that platform requirements are satisfied.
  clear-cache          Clears composer's internal package cache.
  clearcache           Clears composer's internal package cache.
  config               Sets config options.
  create-project       Creates new project from a package into given directory.
  depends              Shows which packages cause the given package to be installed.
  diagnose             Diagnoses the system to identify common errors.
  dump-autoload        Dumps the autoloader.
  dumpautoload         Dumps the autoloader.
  exec                 Executes a vendored binary/script.
  global               Allows running commands in the global composer dir ($COMPOSER_HOME).
  help                 Displays help for a command
  home                 Opens the package's repository URL or homepage in your browser.
  info                 Shows information about packages.
  init                 Creates a basic composer.json file in current directory.
  install              Installs the project dependencies from the composer.lock file if present, or falls back on the composer.json.
  licenses             Shows information about licenses of dependencies.
  list                 Lists commands
  outdated             Shows a list of installed packages that have updates available, including their latest version.
  prohibits            Shows which packages prevent the given package from being installed.
  remove               Removes a package from the require or require-dev.
  require              Adds required packages to your composer.json and installs them.
  run-script           Runs the scripts defined in composer.json.
  search               Searches for packages.
  self-update          Updates composer.phar to the latest version.
  selfupdate           Updates composer.phar to the latest version.
  show                 Shows information about packages.
  status               Shows a list of locally modified packages.
  suggests             Shows package suggestions.
  update               Upgrades your dependencies to the latest version according to composer.json, and updates the composer.lock file.
  upgrade              Upgrades your dependencies to the latest version according to composer.json, and updates the composer.lock file.
  validate             Validates a composer.json and composer.lock.
  why                  Shows which packages cause the given package to be installed.
  why-not              Shows which packages prevent the given package from being installed.

引入一个类库，并使用。

sudo composer require aferrandini/phpqrcode

使用的时候，很简单，只要引入一下自动加载就可以了。

require '../vendor/autoload.php';

\PHPQRCode\QRcode::png("Test", "../tmp/qrcode.png", 'L', 4, 2);

如果是tp等框架，可以将引入部分放在index.php的入口文件，这样每个地方都可以灵活使用插件了。