Get value of dynamically chosen class constant in PHP

Question

I would like to be able to do something like this:

class ThingIDs
{
    const Something = 1;
    const AnotherThing = 2;
}

$thing = \'Something\';
$id = Thi         


        

Answer 1

Helper function

You can use a function like this:

function class_constant($class, $constant)
{
    if ( ! is_string($class)) {
        $class = get_class($class);
    }

    return constant($class . '::' . $constant);
}

It takes two arguments:

• Class name or object instance
• Class constant name

If an object instance is passed, its class name is inferred. If you use PHP 7, you can use ::class to pass appropriate class name without having to think about namespaces.

Examples

class MyClass
{
    const MY_CONSTANT = 'value';
}

class_constant('MyClass', 'MY_CONSTANT'); # 'value'
class_constant(MyClass::class, 'MY_CONSTANT'); # 'value' (PHP 7 only)

$myInstance = new MyClass;
class_constant($myInstance, 'MY_CONSTANT'); # 'value'