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

Can even work with Associative Arrays.. for example in a class.

class Test {

    const 
        CAN = [
            "can bark", "can meow", "can fly"
        ],
        ANIMALS = [
            self::CAN[0] => "dog",
            self::CAN[1] => "cat",
            self::CAN[2] => "bird"
        ];

    static function noParameter() {
        return self::ANIMALS[self::CAN[0]];
    }

    static function withParameter($which, $animal) {
        return "who {$which}? a {$animal}.";
    }

}

echo Test::noParameter() . "s " . Test::CAN[0] . ".<br>";
echo Test::withParameter(
    array_keys(Test::ANIMALS)[2], Test::ANIMALS["can fly"]
);

// dogs can bark.
// who can fly? a bird.

Answer 2

Using explode and implode function we can improvise a solution :

$array = array('lastname', 'email', 'phone');
define('DEFAULT_ROLES', implode (',' , $array));
echo explode(',' ,DEFAULT_ROLES ) [1]; 

This will echo email.

If you want it to optimize it more you can define 2 functions to do the repetitive things for you like this :

//function to define constant
function custom_define ($const , $array) {
    define($const, implode (',' , $array));
}

//function to access constant  
function return_by_index ($index,$const = DEFAULT_ROLES) {
            $explodedResult = explode(',' ,$const ) [$index];
    if (isset ($explodedResult))
        return explode(',' ,$const ) [$index] ;
}

Hope that helps . Happy coding .

Answer 3

You might also explode the array into a series of constants. (a pretty old school solution) After all, the array is constant, so the only reason you need it for, is global, fast, lookup of certain keys.

Hence this:

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

Would turn into:

define('DEFAULT_ROLES_0', 'guy');
define('DEFAULT_ROLES_1', 'development team');

Yes, there's namespace pollution (and a lot of prefixing to prevent it) to take into account.

Answer 4

PHP 7+

As of PHP 7, you can just use the define() function to define a constant array :

define('ANIMALS', [
    'dog',
    'cat',
    'bird'
]);

echo ANIMALS[1]; // outputs "cat"

Answer 5

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'));

Answer 6

Yes, You can define an array as constant. From PHP 5.6 onwards, it is possible to define a constant as a scalar expression, and it is also possible to define an array constant. It is possible to define constants as a resource, but it should be avoided, as it can cause unexpected results.

<?php
    // Works as of PHP 5.3.0
    const CONSTANT = 'Hello World';
    echo CONSTANT;

    // Works as of PHP 5.6.0
    const ANOTHER_CONST = CONSTANT.'; Goodbye World';
    echo ANOTHER_CONST;

    const ANIMALS = array('dog', 'cat', 'bird');
    echo ANIMALS[1]; // outputs "cat"

    // Works as of PHP 7
    define('ANIMALS', array(
        'dog',
        'cat',
        'bird'
    ));
    echo ANIMALS[1]; // outputs "cat"
?>

With the reference of this link

Have a happy coding.