code style section has been added here:
https://github.com/yiisoft/yii2/wiki/Core-framework-code-style#self-vs-static

verification code for properties:
https://gist.github.com/cebe/7566916

Control statements based on the if and elseif constructs must have a single space before the opening parenthesis of the conditional and a single space after the closing parenthesis.

See discussion about exceptions in autoloader here:
https://groups.google.com/forum/?fromgroups#!topic/php-fig/kRTVRSIJ0qE

helps reducing weird error messages.

autoload return value has no effect on other autoloaders
they will only be called based on whether the class has been loaded or
not.

As of PHP 5.3.2 PHP does not send class names with leading \ to
autoload functions.

Removed ltrim for '/' from autoload because it is

1. not needed: https://bugs.php.net/bug.php?id=50731 and
2. possibly wrong behavior: https://bugs.php.net/bug.php?id=51087