I suggest using the phpBB3 Coding Guidelines as a reference document.
Among the areas listed, some which frequently come under contention are:
1. Use of tabs versus spaces for indentation level
2. Number of spaces for indentation level
3. Placement of braces
4. Usage of braces where they are optional
5. Hungarian notation
6. Underscores versus camel case for identifier names
7. Spaces between tokens
8. Alignment of multiline statements
9. Usage of parentheses where they are optional
You should check to see what your current code is like with respect to these issues and decide accordingly (or change your current code if need be). For many of these issues it does not actually matter which way is decided, so long as it is consistently used.