PHP 手册
后退	章 19. 类与对象（PHP 5）	前进

Class Constants

It is possible to define constant values on a per-class basis remaining the same and unchangeable. Constants differ from normal variables in that you don't use the $ symbol to declare or use them. Like static members, constant values cannot be accessed from an instance of the object (using $object::constant).

例子 19-15. Defining and using a constant




<?php



class 

MyClass



{

    const 

constant 

= 

'constant value'

;



    function 

showConstant

() {

        echo  

self

::

constant 

. 

"\n"

;

    }

}



echo 

MyClass

::

constant 

. 

"\n"

;





$class 

= new 

MyClass

();



$class

->

showConstant

();



// echo $class::constant;  is not allowed



?>

后退	起点	前进
Static Keyword	上一级	Class Abstraction