Code as per Drupal standard

Drupal 8

The "Coder" project is transformed from a module to a PHP code sniffer plugin. More info at https://www.drupal.org/node/1419988.

Drupal 7

There is a handy module called Coder, which will verify your custom module/theme against drupal coding standards.

The Coder Upgrade module provides a powerful, automated solution to assist developers wishing to upgrade a module for changes in the Drupal core API (or the API provided by any contributed module into Drupal 7. For an example of this, click here.) This tool relies on the Grammar Parser library to upgrade a module's code files.