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PHP Constants Containing Arrays?

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What is a constant array?

Arrays are Not Constants It does NOT define a constant array. It defines a constant reference to an array. Because of this, we can still change the elements of a constant array.

Can we use const in PHP?

PHP introduced a keyword const to create a constant. The const keyword defines constants at compile time. It is a language construct, not a function. The constant defined using const keyword are case-sensitive.

What are magic constants in PHP?

Magic constants: Magic constants are the predefined constants in PHP which is used on the basis of their use. These constants are created by various extensions. There are nine magic constant in the PHP and all of the constant resolved at the compile-time, not like the regular constant which is resolved at run time.

How do you call a constant in PHP?

A constant is an identifier (name) for a simple value. The value cannot be changed during the script. A valid constant name starts with a letter or underscore (no $ sign before the constant name). Note: Unlike variables, constants are automatically global across the entire script.


Since PHP 5.6, you can declare an array constant with const:

<?php
const DEFAULT_ROLES = array('guy', 'development team');

The short syntax works too, as you'd expect:

<?php
const DEFAULT_ROLES = ['guy', 'development team'];

If you have PHP 7, you can finally use define(), just as you had first tried:

<?php
define('DEFAULT_ROLES', array('guy', 'development team'));

NOTE: while this is the accepted answer, it's worth noting that in PHP 5.6+ you can have const arrays - see Andrea Faulds' answer below.

You can also serialize your array and then put it into the constant:

# define constant, serialize array
define ("FRUITS", serialize (array ("apple", "cherry", "banana")));

# use it
$my_fruits = unserialize (FRUITS);

You can store them as static variables of a class:

class Constants {
    public static $array = array('guy', 'development team');
}
# Warning: array can be changed lateron, so this is not a real constant value:
Constants::$array[] = 'newValue';

If you don't like the idea that the array can be changed by others, a getter might help:

class Constants {
    private static $array = array('guy', 'development team');
    public static function getArray() {
        return self::$array;
    }
}
$constantArray = Constants::getArray();

EDIT

Since PHP5.4, it is even possible to access array values without the need for intermediate variables, i.e. the following works:

$x = Constants::getArray()['index'];

If you are using PHP 5.6 or above, use Andrea Faulds answer

I am using it like this. I hope, it will help others.

config.php

class app{
    private static $options = array(
        'app_id' => 'hello',
    );
    public static function config($key){
        return self::$options[$key];
    }
}

In file, where I need constants.

require('config.php');
print_r(app::config('app_id'));

This is what I use. It is similar to the example provided by soulmerge, but this way you can get the full array or just a single value in the array.

class Constants {
    private static $array = array(0 => 'apple', 1 => 'orange');

    public static function getArray($index = false) {
        return $index !== false ? self::$array[$index] : self::$array;
    }
}

Use it like this:

Constants::getArray(); // Full array
// OR 
Constants::getArray(1); // Value of 1 which is 'orange'