Classes should be given descriptive names.  Avoid using abbreviations
     where possible.  Class names should always begin with an uppercase
     letter.  The PEAR class hierarchy is also reflected in the class name,
     each level of the hierarchy separated with a single underscore.
     Examples of good class names are:
     
    
     Functions and methods should be named using the
     "studly caps" style (also referred to as
     "bumpy case" or "camel caps").
     Functions should in addition have the package name as a prefix,
     to avoid name collisions between packages.  The initial letter of
     the name (after the prefix) is lowercase, and each letter that
     starts a new "word" is capitalized.  Some examples:
     
    
     Private class members (meaning class members that are intended
     to be used only from within the same class in which they are
     declared; PHP does not yet support truly-enforceable private
     namespaces) are preceded by a single underscore. For example:
     
    
    
Note: The following applies to PHP5.
     Protected class members (meaning class members that are intended
     to be used only from within the same class in which they are
     declared or from subclasses that extend it) are not preceded by a single
     underscore. For example:
     
    
     Constants should always be all-uppercase, with underscores to
     separate words.  Prefix constant names with the uppercased name
     of the class/package they are used in. For example, the constants
     used by the DB:: package all begin with
     DB_.
     
Note: 
       The true, false and
       null constants are excepted from the all-uppercase
       rule, and must always be lowercase.
      
     If your package needs to define global variables, their name
     should start with a single underscore followed by the package
     name and another underscore.  For example, the PEAR package uses
     a global variable called $_PEAR_destructor_object_list.