constant

Returns the value of a constant

&reftitle.description; `mixed` `constant` `string` `name`

Return the value of the constant indicated by `name`.

`constant` is useful if you need to retrieve the value of a constant, but do not know its name. I.e. it is stored in a variable or returned by a function.

This function works also with class constants and enum cases.

&reftitle.parameters;

`name`

- The constant name.

&reftitle.returnvalues;

Returns the value of the constant.

&reftitle.errors;

If the constant is not defined, an `Error` exception is thrown. Prior to PHP 8.0.0, an `E_WARNING` level error was generated in that case.

&reftitle.changelog;

&Version; | &Description;
8.0.0 | If the constant is not defined, `constant` now throws an `Error` exception; previously an `E_WARNING` was generated, and &null; was returned.

&reftitle.examples;

### Using `constant` with Constants

    <?php

    define("MAXSIZE", 100);

    echo MAXSIZE;
    echo constant("MAXSIZE"); // same thing as the previous line

    interface bar {
        const test = 'foobar!';
    }

    class foo {
        const test = 'foobar!';
    }

    $const = 'test';

    var_dump(constant('bar::'. $const)); // string(7) "foobar!"
    var_dump(constant('foo::'. $const)); // string(7) "foobar!"

    ?>

### Using `constant` with Enum Cases (as of PHP 8.1.0)

    <?php

    enum Suit
    {
        case Hearts;
        case Diamonds;
        case Clubs;
        case Spades;
    }

    $case = 'Hearts';

    var_dump(constant('Suit::'. $case)); // enum(Suit::Hearts)

    ?>

&reftitle.seealso;

- `define`
- `defined`
- `get_defined_constants`
- The section on Constants