Use uniform coding style across all the custom components and modules in your web project.

To formalize, this rule implies: 1) the coding style standard must exist -in any form; 2) all the developers obey that standard. You might want to start with Bitrix Framework PHP Source Code Formatting Guidelines, or ZendFramework standard.

Sticking to the coding style standard improves code quality and readability, helps avoid errors and reduces further maintenance and development cost. Allowing the developers to knock themselves out on the coding style will unavoidably lead to poor quality, intricate code that only the authors can make out. It is almost impossible to develop projects based on such code further.

Ensure all the developers involved in the project have and adhere to an established coding style standard consistent with the Bitrix guidelines.