Do you think that white space matters? Does your boss or your client insist on "TRUE" instead of "true", or vice versa? Are you contributing to an open-source project that has developed its own coding standards?
If any of these apply, and if you write PHP code, then PHP CodeSniffer can help keep you on track by telling you where your code does not match the standard. Recent versions of this tool can automatically fix many violations.
I will use examples based on Drupal and WordPress.