Note that if you are using Eclipse or Zend IDE you can benefit from automatic tools that makes the respect of a standard less costly. You can also use a continuous integration tool like Hudson or PHPUndercontrol.
- PDT is a cool editor for PHP
- PDT-Tools are some plugins for PDT with an automatic formatting tool
- DTLK (Dynamic Toolkit Library) can be used to launch some external scripts to check your files.
You can also have a look at PHP Checkstyle which I think is easier to configure (disclaimer : I've worked on it)
Some other tools are listed on the "documentation" page of the web site.
