Converting a constant array to a constant string

Question

I've this code:

const TYPE_A = 'a';
const TYPE_B = 'b';
const TYPE_C = 'c';

const TYPE_ARRAY = [
TYPE_A,
TYPE_B,
TYPE_C,
];

I use the TYPE_ARRAY to check if a type is valid by using in_array(). But I also need to do a regex check, but I can't use this array directly for that. I need a string in the form: "a|b|c", which is equivalent to:

implode('|', TYPE_ARRAY);

But in stead of doing this:

const TYPE_REGEX_STR = "a|b|c";

I wonder if it wouldn't be possible to convert the const TYPE_ARRAY automatically to a constant with the regex. So something like this:

const TYPE_REGEX_STR = implode('|', TYPE_ARRAY);

I know that this last example is not possible, but is there a another way do this?

This might seem silly, but when you have an array with many possible types, it would be better to create the const TYPE_REGEX_STR based on the const TYPE_ARRAY instead of defining it separately. In that way it would be easier to add a new type: just add it to the array and the regex string is made automatically.

Btw I need TYPE_REGEX_STR as a constant because Symfony can use a constant in the route requirements, but not a static function.

did you tried use symfony.com/doc/current/routing/conditions.html? — myxaxa
– myxaxa, Commented May 29, 2019 at 14:13

bassxzero · Accepted Answer · 2019-05-29 13:25:12Z

3

You could use define

<?php

const TYPE_A = 'a';
const TYPE_B = 'b';
const TYPE_C = 'c';

const TYPE_ARRAY = [
TYPE_A,
TYPE_B,
TYPE_C,
];

define ( 'TYPE_REGEX_STR' , implode('|', TYPE_ARRAY) );

echo TYPE_REGEX_STR;

answered May 29, 2019 at 13:25

bassxzero

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1 Comment

L.A. Rabida Over a year ago

This works worderfully, BUT it appears that Symfony can only work with class constants in the route requirement, so using define at runtime (e.g. in the __contruct function of the controller class) does not work. Pity! But thanks for your help.

Carlos Alves Jorge · Accepted Answer · 2019-05-29 13:25:35Z

2

You will want to use define

define( 'TYPE_REGEX_STR', implode('|', TYPE_ARRAY) );

answered May 29, 2019 at 13:25

Carlos Alves Jorge

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2 Comments

L.A. Rabida Over a year ago

Thanks, sounds great, but the problem is that Symfony can only use a class constant in a route requirement, and since define() is used at runtime, I can't use it for that I'm sorry to say.

Carlos Alves Jorge Over a year ago

Check here. Maybe you can create a class and method stackoverflow.com/questions/18079131/…

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