Constant expressions in PHP 5.5 or before

Question

I'm working on a legacy PHP codebase that runs on PHP 5.4. I want to derive class-specific constants or properties based on a common constant. So for instance in PHP 5.6 or later I'd do:

config.php

define('CONFIG_DIR', 'PATH_TO_CONFIG_DIR');

MyClass.php

class MyClass {
     const FILE_A = CONFIG_DIR . '/fileA';
     const FILE_B = CONFIG_DIR . '/fileB';
}

But constant expressions are only allowed since PHP 5.6.

https://www.php.net/manual/en/migration56.new-features.php

So in PHP 5.4 what are the options that I could follow to derive sub-values based on a common constant within the class?

how about using `$GLOBALS`? https://www.php.net/manual/en/reserved.variables.globals.php — Raptor, Nov 21 '22 at 06:39
@Raptor Thanks for the suggestions. But in that case I can't define those new variables as constants though. — Gayan Weerakutti, Nov 21 '22 at 06:56
Strange that the question (https://stackoverflow.com/questions/18079131/best-workaround-to-create-a-php-class-constant-from-an-expression) seems to give all the options in the question, not sure if that could be reworked to a proper reference. — Nigel Ren, Nov 21 '22 at 07:14

score 4 · Accepted Answer · answered Nov 21 '22 at 06:53

4

define could be an option.

define('CONFIG_DIR', 'PATH_TO_CONFIG_DIR');
define('CONFIG_DIR_FILE_A', CONFIG_DIR . '/fileA');
define('CONFIG_DIR_FILE_B', CONFIG_DIR . '/fileB');
class MyClass {
     const FILE_A = CONFIG_DIR_FILE_A;
     const FILE_B = CONFIG_DIR_FILE_B;
}

answered Nov 21 '22 at 06:53

shingo

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To obtain the constant `FILE_A` from `MyClass`, [Relection](https://www.php.net/manual/en/book.reflection.php) can be used in PHP 5.4: `$c = new ReflectionClass('MyClass'); echo $c->getConstants()['FILE_A'];` – Raptor Nov 21 '22 at 07:03

Constant expressions in PHP 5.5 or before

1 Answers1