constant

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

constantReturns the value of a constant

Description

constant(string $name): mixed

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.

Parameters

name

The constant name.

Return Values

Returns the value of the constant.

Errors/Exceptions

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.

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.

Examples

Example #1 constant() example

<?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!"

?>

See Also