I have just extended my PHP coding standard guidelines with these rules about variable naming:

• Remember this is PHP, not Microsoft Visual C++. There is actually little value in naming variables something like strFullTitle . Something like full_title is definitely enough and much easier to read!
• As an exception to the previous rule, we'll preferably prefix private or protected member variables of a class with an underscore as in _full_title. This serves as an easy reminder that the variable is not designed to be called in any other ways as in $this->_full_title .
• Class names should start with a capital, as in Book .

• Variable names should be all lowercase, as in $title = 'A brand new day'; except when they are object references as in:

  $a_Book = & new Book( 'A brand new day' );

• When naming object references, always end their name with the name of the class as in $a_Book or $another_Book instead of Book_to_read for example. This allows to easily search & find all calls to a given method of a given class. You could for exampel easily search on this string: "Book->get_title(" .