(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)
constant — Returns the value of a constant
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.
nameThe constant name.
Returns the value of the constant.
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.
| 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. |
Example #1 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!"
?>Example #2 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)
?>