A static properties
Use keyword static properties and methods defined directly belong to the class, the object does not go into
Access class static property static property class name :: 1 :: scope resolution operator before static properties plus $ 2.
Static methods and static properties of the same attributes
Static methods can not use the keyword $ this $ this is an instance of an object and the object can not access the static member
Static class members operating inside the box using self self directed class itself
Second, the constant
Class keyword, sonst defined constant member, visit the class constants, using self
Constant object can not operate
Third, Object clone
1, a variable assignment between the object and is not cloned, but the object will be assigned to the variable address memory
2, js create objects cloned by
3, php objects cloned by clone keyword
By the time the keyword clone clone, in fact, hidden function function _clone call ()
If the class instance object generated not to be cloned, modified to hide access modifier function function _clone () in front of it as protected
