Why does composer not work with core composer.json file when adding new libraries? When you download the source from here, and run composer:

php composer.phar require facebook/graph-sdk


I get:

    You are running Composer with SSL/TLS protection disabled.
Using version ^5.6 for facebook/graph-sdk
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.4
9m

  Problem 1
    - Conclusion: don't install symfony/http-kernel v2.8.27
    - ...
    - Conclusion: don't install symfony/http-kernel v2.8.5
    - Conclusion: remove symfony/http-kernel v2.8.4
    - Conclusion: don't install symfony/http-kernel v2.8.4
    - ...
    - Installation request for symfony/http-kernel ~2.8 -&gt; satisfiable by symfony/http-kernel[2.8.x-dev, v2.8.0, v2.8.0-BETA1, v2.8.1, v2.8.10, v2.8.11, v2.8.12, v2.8.13, v2.8.14, v2.8.15, v2.8.16, v2.8.17, v2.8.18, v2.8.19, v2.8.2, v2.8.20, v2.8.21, v2.8.22, v2.8.23, v2.8.24, v2.8.25, v2.8.26, v2.8.27, v2.8.3, v2.8.4, v2.8.5, v2.8.6, v2.8.7, v2.8.8, v2.8.9].
    - Conclusion: don't install symfony/debug v3.0.9
    - symfony/http-kernel 2.8.x-dev requires symfony/debug ^2.6.2 -&gt; satisfiable by symfony/debug[v2.7.6, 2.6.x-dev, 2.7.x-dev, 2.8.x-dev, v2.6.10, v2.6.11, v2.6.12, v2.6.13, v2.6.2, v2.6.3, v2.6.4, v2.6.5, v2.6.6, v2.6.7, v2.6.8, v2.6.9, v2.7.0, v2.7.0-BETA1, v2.7.0-BETA2, v2.7.1, v2.7.10, v2.7.11, v2.7.12, v2.7.13, v2.7.14, v2.7.15, v2.7.16, v2.7.17, v2.7.18, v2.7.19, v2.7.2, v2.7.20, v2.7.21, v2.7.22, v2.7.23, v2.7.24, v2.7.25, v2.7.26, v2.7.27, v2.7.28, v2.7.29, v2.7.3, v2.7.30, v2.7.31, v2.7.32, v2.7.33, v2.7.34, v2.7.4, v2.7.5, v2.7.7, v2.7.8, v2.7.9, v2.8.0, v2.8.0-BETA1, v2.8.1, v2.8.10, v2.8.11, v2.8.12, v2.8.13, v2.8.14, v2.8.15, v2.8.16, v2.8.17, v2.8.18, v2.8.19, v2.8.2, v2.8.20, v2.8.21, v2.8.22, v2.8.23, v2.8.24, v2.8.25, v2.8.26, v2.8.27, v2.8.3, v2.8.4, v2.8.5, v2.8.6, v2.8.7, v2.8.8, v2.8.9].
    - Can only install one of: symfony/debug[v3.0.9, v2.7.6].
    - ...
    - Can only install one of: symfony/debug[v2.8.9, v3.0.9].
    - Installation request for symfony/debug (locked at v3.0.9) -&gt; satisfiable by symfony/debug[v3.0.9].

Installation failed, reverting ./composer.json to its original content.


Surely the core composer file that comes with Drupal can work with the facebook SDK. What am I missing?
Hope it helps someone else. The issue was that I only updated drupal's /core folder, not composer.json. So I had a very old composer file. When I updated it with the composer.json from the latest D8 download, things started working again.