PHP: undefined constant while defining it

Question

I'm getting the following error in PHP:

Notice: Use of undefined constant CONSTANT

on the exact line where I define it:

define(CONSTANT, true);

What am I doing wrong? I defined it, so why does it say "Undefined constant"?

You can't define CONSTANT, it's just that; a CONSTANT - RTMs http://php.net/manual/en/function.constant.php - http://php.net/manual/en/function.define.php — Funk Forty Niner, Nov 25 '16 at 14:19
Possible duplicate http://stackoverflow.com/questions/2447791/define-vs-const/3193704 — TZubiri, Nov 25 '16 at 14:20
@TomasZubiri It's not a duplicate of that question; I did not seek for the difference between define vs const, I was asking what was wrong with my code. — Sherida van den Bent, Nov 28 '16 at 19:03

score 11 · Accepted Answer · edited Nov 25 '16 at 14:19

11

You need to quote the string which becomes a constant

define('CONSTANT', true);

edited Nov 25 '16 at 14:19

RiggsFolly

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answered Nov 25 '16 at 14:19

donald123

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That was it! Thank you very much! – Sherida van den Bent Nov 25 '16 at 15:39

score 6 · Answer 2 · answered Nov 25 '16 at 14:24

6

The best way to understand what are you doing wrong is to read PHP manual.

Here is definition of define function.

bool define ( string $name , mixed $value [, bool $case_insensitive = false ] )

So the first argument must be a string.

answered Nov 25 '16 at 14:24

phpio.net

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score 2 · Answer 3 · answered Nov 25 '16 at 14:20

2

If you write it like that you are using the value of an already defined constant as a constant name.

What you want to do is to pass the name as a string:

define('CONSTANT', true);

answered Nov 25 '16 at 14:20

Ibrahim

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Poiz · Answer 4 · 2016-11-25T17:53:08.440

Although not really, strictly relevant to your case, it is most desirable to first check that a CONSTANT has not been previously defined before (re)defining it.... It is also important to keep in mind that defining CONSTANTS using define requires that the CONSTANT to be defined is a STRING ie. enclosed within Quotes like so:

<?php

    // CHECK THAT THE CONSTANTS HASN'T ALREADY BEEN DEFINED BEFORE DEFINING IT...
    // AND BE SURE THE NAME OF THE CONSTANT IS WRAPPED WITHIN QUOTES...
    defined('A_CONSTANT') or define('A_CONSTANT', 'AN ALPHA-NUMERIC VALUE', true);

    // BUT USING THE CONSTANT, YOU NEED NOT ENCLOSE IT WITHIN QUOTES.
    echo A_CONSTANT;  //<== YIELDS::   "AN ALPHA-NUMERIC VALUE"

score 0 · Answer 5 · answered Nov 25 '16 at 14:39

See below currect way to define constant

define('Variable','Value',case-sensitive);

Here Variable ==> Define your Constant Variable Name
Here Value ==> Define Constant value
Here case-sensitive Defult value 'false', Also you can set value 'true' and 'false'

PHP: undefined constant while defining it

5 Answers5