Update: people also use PSR nowadays a lot
Zend Framework and PEAR standards are pretty much the most common coding conventions. If your company adopted another one, stick to the your company's convention though. Better than having no convention at all. And they only work if everyone sticks to them.
Also see:
- Which Coding convention to follow for PHP?
- PHP best practices for naming conventions
- PHP coding conventions?
Basically, all of the major frameworks have a coding convention somewhere in their documentation. The official (but mostly unknown IMO) PHP Coding Guidelines can be found at
- http://news.php.net/php.standards/2
If you need to validate code against a coding convention, consider using CodeSniffer. Some IDEs also offer automatic sourcecode formatting by templates. For instance Zend Studio has the ZF coding guidelines built-in, so it's just a click to format code to that convention.