PHP Constants Containing Arrays?

Question

This failed:

 define('DEFAULT_ROLES', array('guy', 'development team'));

Apparently, constants can't hold arrays. What is the best way to get around this?

define('DEFAULT_ROLES', 'guy|development team');

//...

$default = explode('|', DEFAULT_ROLES);

This seems like unnecessary effort.

Answer 1

You can store it as a JSON string in a constant. And application point of view, JSON can be useful in other cases.

define ("FRUITS", json_encode(array ("apple", "cherry", "banana")));    
$fruits = json_decode (FRUITS);    
var_dump($fruits);

Answer 2

I know it's a bit old question, but here is my solution:

<?php
class Constant {

    private $data = [];

    public function define($constant, $value) {
        if (!isset($this->data[$constant])) {
            $this->data[$constant] = $value;
        } else {
            trigger_error("Cannot redefine constant $constant", E_USER_WARNING);
        }
    }

    public function __get($constant) {
        if (isset($this->data[$constant])) {
            return $this->data[$constant];
        } else {
            trigger_error("Use of undefined constant $constant - assumed '$constant'", E_USER_NOTICE);
            return $constant;
        }
    }

    public function __set($constant,$value) {
        $this->define($constant, $value);
    }

}
$const = new Constant;

I defined it because I needed to store objects and arrays in constants so I installed also runkit to php so I could make the $const variable superglobal.

You can use it as $const->define("my_constant",array("my","values")); or just $const->my_constant = array("my","values");

To get the value just simply call $const->my_constant;

Answer 3

If you are looking this from 2009, and you don't like AbstractSingletonFactoryGenerators, here are a few other options.

Remember, arrays are "copied" when assigned, or in this case, returned, so you are practically getting the same array every time. (See copy-on-write behaviour of arrays in PHP.)

function FRUITS_ARRAY(){
  return array('chicken', 'mushroom', 'dirt');
}

function FRUITS_ARRAY(){
  static $array = array('chicken', 'mushroom', 'dirt');
  return $array;
}

function WHAT_ANIMAL( $key ){
  static $array = (
    'Merrick' => 'Elephant',
    'Sprague' => 'Skeleton',
    'Shaun'   => 'Sheep',
  );
  return $array[ $key ];
}

function ANIMAL( $key = null ){
  static $array = (
    'Merrick' => 'Elephant',
    'Sprague' => 'Skeleton',
    'Shaun'   => 'Sheep',
  );
  return $key !== null ? $array[ $key ] : $array;
}

Answer 4

define('MY_ARRAY_CONSTANT_DELIMETER', '|');       
define('MY_ARRAY',implode(MY_ARRAY_CONSTANT_DELIMETER,array(1,2,3,4)));

//retrieving the array
$my_array = explode(MY_ARRAY_CONSTANT_DELIMETER, MY_ARRAY);

Answer 5

Starting with PHP 5.6, you can define constant arrays using const keyword like below

const DEFAULT_ROLES = ['test', 'development', 'team'];

and different elements can be accessed as below:

echo DEFAULT_ROLES[1]; 
....

Starting with PHP 7, constant arrays can be defined using define as below:

define('DEFAULT_ROLES', [
    'test',
    'development',
    'team'
]);

and different elements can be accessed same way as before.

Answer 6

Doing some sort of ser/deser or encode/decode trick seems ugly and requires you to remember what exactly you did when you are trying to use the constant. I think the class private static variable with accessor is a decent solution, but I'll do you one better. Just have a public static getter method that returns the definition of the constant array. This requires a minimum of extra code and the array definition cannot be accidentally modified.

class UserRoles {
    public static function getDefaultRoles() {
        return array('guy', 'development team');
    }
}

initMyRoles( UserRoles::getDefaultRoles() );

If you want to really make it look like a defined constant you could give it an all caps name, but then it would be confusing to remember to add the '()' parentheses after the name.

class UserRoles {
    public static function DEFAULT_ROLES() { return array('guy', 'development team'); }
}

//but, then the extra () looks weird...
initMyRoles( UserRoles::DEFAULT_ROLES() );

I suppose you could make the method global to be closer to the define() functionality you were asking for, but you really should scope the constant name anyhow and avoid globals.