使用包含常量名称的简单变量访问类常量

Question

I'm trying to access a class constant in one of my classes:

const MY_CONST = "value";

If I have a variable which holds the name of this constant like this:

$myVar = "MY_CONST";

Can I access the value of MY_CONST somehow?

self::$myVar

does not work obviously because it is for static properties. Variable variables does not work either.

Answer 1

There are two ways to do this: using the constant function or using reflection.

Constant Function

The constant function works with constants declared through define as well as class constants:

class A
{
    const MY_CONST = 'myval';

    static function test()
    {
        $c = 'MY_CONST';
        return constant('self::'. $c);
    }
}

echo A::test(); // output: myval

Reflection Class

A second, more laborious way, would be through reflection:

$ref = new ReflectionClass('A');
$constName = 'MY_CONST';
echo $ref->getConstant($constName); // output: myval