It's pretty common to find servers with PHP 5.3 version installed on it, which isn't supported by the community anymore.
So here it is a tool that read all your files and rewrite code using PHP 5.3 standards: https://github.com/endel/php-code-downgrade/
# clone the repository
git clone https://github.com/endel/php-code-downgrade.git && cd php-code-downgrade
# install composer dependencies
# run against your codebase
The advantages of using this is that you can write modern code without worrying about legacy PHP version support.