title: Composer autoloader not loading GuzzleHttp\ClientInterface
body: <p>I'm trying to use <a href="http://guzzle.readthedocs.org/en/latest/" rel="nofollow">Guzzle</a>, but I'm getting the following <strong>fatal error:</strong></p>
  
  <blockquote>
    <p>Fatal error: Class 'GuzzleHttp\ClientInterface' not found in
    /var/www/myapp/vendor/guzzlehttp/guzzle/src/functions.php on line 13</p>
  </blockquote>
  
  <p>I'm autoloading with composer autoloader:</p>
  
  <pre><code>require 'vendor/autoload.php';
  
  use Guzzle\Http\Client;
  
  $client = new Client();
  
  $requests = Array(
      $client-&gt;createRequest('GET', 'ams1.myapp.com:8080/api/ffmpeg_make_snapshots.php'),
      $client-&gt;createRequest('GET', 'ams2.myapp.com:8080/api/ffmpeg_make_snapshots.php'),
      $client-&gt;createRequest('GET', 'ams3.myapp.com:8080/api/ffmpeg_make_snapshots.php')
  );
  
  $client-&gt;sendAll($requests);
  </code></pre>
  
  <p>What is happening?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>My composer.json:</p>
  
  <pre><code>{
      "require": {
          "guzzlehttp/guzzle": "~4"
      }
  }
  </code></pre>
  
  <p><strong>EDIT 2</strong></p>
  
  <p>My composer.lock</p>
  
  <pre><code>
  {
      "_readme": [
          "This file locks the dependencies of your project to a known state",
          "Read more about it at http://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file"
      ],
      "hash": "33c003b6e3e2dc0144146f9b652a6719",
      "packages": [
          {
              "name": "guzzlehttp/guzzle",
              "version": "4.0.0",
              "source": {
                  "type": "git",
                  "url": "https://github.com/guzzle/guzzle.git",
                  "reference": "4063f08ca434efac12bf7a3db0d370b1c451345b"
              },
              "dist": {
                  "type": "zip",
                  "url": "https://api.github.com/repos/guzzle/guzzle/zipball/4063f08ca434efac12bf7a3db0d370b1c451345b",
                  "reference": "4063f08ca434efac12bf7a3db0d370b1c451345b",
                  "shasum": ""
              },
              "require": {
                  "guzzlehttp/streams": "1.*",
                  "php": ">=5.4.0"
              },
              "require-dev": {
                  "ext-curl": "*",
                  "phpunit/phpunit": "4.*",
                  "psr/log": "~1"
              },
              "type": "library",
              "extra": {
                  "branch-alias": {
                      "dev-master": "4.0.x-dev"
                  }
              },
              "autoload": {
                  "psr-4": {
                      "GuzzleHttp\\": "src/"
                  },
                  "files": [
                      "src/functions.php"
                  ]
              },
              "notification-url": "https://packagist.org/downloads/",
              "license": [
                  "MIT"
              ],
              "authors": [
                  {
                      "name": "Michael Dowling",
                      "email": "mtdowling@gmail.com",
                      "homepage": "https://github.com/mtdowling"
                  }
              ],
              "description": "Guzzle is a PHP HTTP client library and framework for building RESTful web service clients",
              "homepage": "http://guzzlephp.org/",
              "keywords": [
                  "client",
                  "curl",
                  "framework",
                  "http",
                  "http client",
                  "rest",
                  "web service"
              ],
              "time": "2014-03-29 23:11:36"
          },
          {
              "name": "guzzlehttp/streams",
              "version": "1.4.0",
              "source": {
                  "type": "git",
                  "url": "https://github.com/guzzle/streams.git",
                  "reference": "3b761a328e5ed6ed519e960aded95d7acbe77894"
              },
              "dist": {
                  "type": "zip",
                  "url": "https://api.github.com/repos/guzzle/streams/zipball/3b761a328e5ed6ed519e960aded95d7acbe77894",
                  "reference": "3b761a328e5ed6ed519e960aded95d7acbe77894",
                  "shasum": ""
              },
              "require": {
                  "php": ">=5.4.0"
              },
              "require-dev": {
                  "phpunit/phpunit": "~4.0"
              },
              "type": "library",
              "extra": {
                  "branch-alias": {
                      "dev-master": "1.4.x-dev"
                  }
              },
              "autoload": {
                  "psr-4": {
                      "GuzzleHttp\\Stream\\": "src/"
                  },
                  "files": [
                      "src/functions.php"
                  ]
              },
              "notification-url": "https://packagist.org/downloads/",
              "license": [
                  "MIT"
              ],
              "authors": [
                  {
                      "name": "Michael Dowling",
                      "email": "mtdowling@gmail.com",
                      "homepage": "https://github.com/mtdowling"
                  }
              ],
              "description": "Provides a simple abstraction over streams of data (Guzzle 4+)",
              "homepage": "http://guzzlephp.org/",
              "keywords": [
                  "Guzzle",
                  "stream"
              ],
              "time": "2014-07-19 18:43:42"
          }
      ],
      "packages-dev": [],
      "aliases": [],
      "minimum-stability": "stable",
      "stability-flags": [],
      "platform": [],
      "platform-dev": []
  }
  </code></pre>
  
  <p><strong>EDIT 3</strong></p>
  
  <p>composer config -l output:</p>
  
  <pre><code>
  [repositories.packagist.type] composer
  [repositories.packagist.url] https?://packagist.org
  [repositories.packagist.allow_ssl_downgrade] true
  [process-timeout] 300
  [use-include-path] false
  [preferred-install] auto
  [notify-on-install] true
  [github-protocols] [git, https]
  [vendor-dir] vendor
  [bin-dir] {$vendor-dir}/bin (vendor/bin)
  [cache-dir] C:/Users/User/AppData/Local/Composer
  [cache-files-dir] {$cache-dir}/files (C:/Users/User/AppData/Local/Composer/files)
  [cache-repo-dir] {$cache-dir}/repo (C:/Users/User/AppData/Local/Composer/repo)
  [cache-vcs-dir] {$cache-dir}/vcs (C:/Users/User/AppData/Local/Composer/vcs)
  [cache-ttl] 15552000
  [cache-files-ttl] 15552000
  [cache-files-maxsize] 300MiB (314572800)
  [discard-changes] false
  [prepend-autoloader] true
  [github-domains] [github.com]
  [home] C:/Users/User/AppData/Roaming/Compose
  </code></pre>