Composer is package management software used by PHP. This allow you to use PHP code written by others to be used in your PHP projects.

Install Composer in Ubuntu/Lubuntu

Code:
curl -s https://getcomposer.org/installer | php
sudo mv composer.phar /usr/local/bin/composer
sudo chmod +x /usr/local/bin/composer
This work on most Linux servers.

To verify if composer working, run composer, you will see something like

Code:
[email protected]:~ $ composer
   ______
  / ____/___  ____ ___  ____  ____  ________  _____
 / /   / __ \/ __ `__ \/ __ \/ __ \/ ___/ _ \/ ___/
/ /___/ /_/ / / / / / / /_/ / /_/ (__  )  __/ /
\____/\____/_/ /_/ /_/ .___/\____/____/\___/_/
                    /_/
Composer version 1.0-dev (ffffab37a294f3383c812d0329623f0a4ba45387) 2014-11-05 06:04:18

Usage:
  [options] command [arguments]

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

Available commands:
  about            Short information about Composer
  archive          Create an archive of this composer package
  browse           Opens the package's repository URL or homepage in your browser.
  clear-cache      Clears composer's internal package cache.
  clearcache       Clears composer's internal package cache.
  config           Set config options
  create-project   Create new project from a package into given directory.
  depends          Shows which packages depend on the given package
  diagnose         Diagnoses the system to identify common errors.
  dump-autoload    Dumps the autoloader
  dumpautoload     Dumps the autoloader
  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.
  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         Show information about licenses of dependencies
  list             Lists commands
  remove           Removes a package from the require or require-dev
  require          Adds required packages to your composer.json and installs them
  run-script       Run the scripts defined in composer.json.
  search           Search for packages
  self-update      Updates composer.phar to the latest version.
  selfupdate       Updates composer.phar to the latest version.
  show             Show information about packages
  status           Show a list of locally modified packages
  update           Updates your dependencies to the latest version according to composer.json, and updates the composer.lock file.
  validate         Validates a composer.json
[email protected]:~ $