Issue #2707163 by quietone, chishah92, jhodgdon, AndrewHD, xjm, dww,...

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Drupal contains an extensive API that allows you to add to and modify the

functionality of your site. The API consists of "hooks", which allow modules to

react to system events and customize Drupal's behavior, and functions that

standardize common operations such as database queries and form generation. The

flexible hook architecture means that you should never need to directly modify

the files that come with Drupal core to achieve the functionality you want;

instead, functionality modifications take the form of modules.

functionality of your site. This means that you should never need to directly

modify the files that come with Drupal core to achieve the behavior you want;

instead, modifications take the form of modules.

When you need new functionality for your Drupal site, search for existing

contributed modules. If you find a module that matches except for a bug or an

when nothing existing comes close to what you need.

More about developing:

 * Extending and altering Drupal

   https://api.drupal.org/api/drupal/core%21core.api.php/group/extending

 * Search for existing contributed modules:

   https://www.drupal.org/project/project_module

 * Contribute a patch:

 * Follow programming best practices:

   https://www.drupal.org/docs/develop/standards

 * Refer to the API documentation:

   https://api.drupal.org/api/drupal/9

   https://api.drupal.org

 * Learn from documented Drupal API examples:

   https://www.drupal.org/project/examples