Destroy defined key with define function

Question

How I can destroy an const? I tried unset( KEY ), but not work.

<?php
define('KEY', 'value');
echo KEY; //output value
unset( KEY ); //no work
?>

The whole point of a constant is that it is immutable after it has been defined. Since you cannot change its value, there is little point to being able to unset it. — Michael Berkowski, Jun 23 '12 at 03:24

score 8 · Answer 1 · answered Jun 23 '12 at 03:24

8

Constants created with define() can't be undefined once created.

answered Jun 23 '12 at 03:24

matt3141

score 4 · Answer 2 · answered Jun 23 '12 at 03:27

4

The closest you can get to unsetting a constant is use of the RunKit extension. See http://php.net/manual/en/function.runkit-constant-remove.php

answered Jun 23 '12 at 03:27

Menztrual · Answer 3 · 2012-06-23T03:33:49.327

0

You can't destroy a constant or alter its value during run time.

Your best option is to use a variable.

$key = "value";

echo $key;

unset($key);

Not to mention; If you could, it would be extremely bad practice :P

edited Jun 23 '12 at 03:33

answered Jun 23 '12 at 03:25

Menztrual

score 0 · Answer 4 · answered Jun 23 '12 at 07:19

0

This isn't possible. If you could unset a constant then it wouldn't be very constant!

If you really need to delete this constant you probably need to use a variable.

answered Jun 23 '12 at 07:19

user1474090

1

stop assuming what we need to do. There are more people, works, and function asked of programmers than you can think of. – Félix Adriyel Gagnon-Grenier Apr 16 '14 at 18:07

score 0 · Answer 5 · answered Jan 15 '14 at 17:39

0

You can't destroy or unset a Constant in PHP and it's value can't change along de Script.

answered Jan 15 '14 at 17:39

DrWaky

score 0 · Answer 6 · answered Nov 29 '18 at 11:39

0

Use

runkit_constant_remove ( 'KEY' );

answered Nov 29 '18 at 11:39

nacesprin

6 Answers6