PHP-值从变量到常量 [英] PHP - value from variable to constant

问题描述

我正在用PHP学习OOP，我想将值从变量转换为类常量.我该怎么办?

I'm learning OOP in PHP and I want to put value from variable to class constant. How can I do that?

这是我的代码(不起作用！):

This is my code (not working!):

class Dir {

const ROOT = $_SERVER['DOCUMENT_ROOT']."project/";

function __construct() {

}
}

有什么解决方法，如何从变量中获取值，添加字符串并将其置于常量中-在OOP中?

Is there any solution, how to take value from variable, add string and put it to constant - in OOP?

推荐答案

从手册页 http://www.php.net/manual/en/language.oop5.constants.php ，您会发现:

The value must be a constant expression, not (for example) a variable, a property, a result of a mathematical operation, or a function call. 

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