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# Object 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 the 節 called Static Keyword members, constant values can not be accessed with a variable that is an instance of the object.

示範 14-9.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 */ ?>`

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