Making code PSR-2 compliant

The changes in the PR are the result of Running [php-cs-fixer](https://github.com/fabpot/PHP-CS-Fixer) with `--level=psr2`. The exact command that was run in the project's base directory was:

    php-cs-fixer fix --level psr2 .

This brought the entire project's PHP code in compliance with the [PSR-2 Coding Style Guide](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md).