如何检查PHP中是否存在常量 [英] How to check if a constant exists in PHP

问题描述

因此，我正在使用一个名为 fuelphp 的PHP框架，并且此页面是 HTML 文件，因此无法在其中使用PHP.我还有另一个带有顶栏的文件，我的HTML文件将通过ajax调用.

So I'm using a PHP framework called fuelphp, and I have this page that is an HTML file, so I can't use PHP in it. I have another file that has a top bar in it, which my HTML file will call through ajax.

如何检查PHP中是否存在常量?
我要检查fuelphp框架文件的位置.

How do I check if a constant exists in PHP?
I want to check for the the fuelphp framework file locations.

这些是我需要检查的常量(实际上，我只需要检查其中之一):

These are the constants I need to check for (actually, I only have to check one of them):

define('DOCROOT', __DIR__.DIRECTORY_SEPARATOR);
    define('APPPATH', realpath(__DIR__.'/fuel/app/').DIRECTORY_SEPARATOR);
    define('PKGPATH', realpath(__DIR__.'/fuel/packages/').DIRECTORY_SEPARATOR);
    define('COREPATH', realpath(__DIR__.'/fuel/core/').DIRECTORY_SEPARATOR);                    
    require APPPATH.'bootstrap.php';

我意识到这些不是变量，而是常量...

edit:
I realized that these aren't variables they are constants...

推荐答案

首先，这些不是变量，而是常量.

First, these are not variables, but constants.

您可以使用 defined() 函数检查它们的存在:

And you can check their existence by using the defined() function :

bool defined ( string $name )

检查给定常量是否存在并已定义.

Checks whether the given constant exists and is defined.

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