If you want to return the constants defined inside a class then you can also define an internal method as follows:

<?php
class myClass {
    const NONE = 0;
    const REQUEST = 100;
    const AUTH = 101;

    // others...

    static function getConstants() {
        $oClass = new ReflectionClass(__CLASS__);
        return $oClass->getConstants();
    }
}
?>

If you want to define a static getConstants() function which works with inheritance you can do the following:

<?php

abstract class AbstractClass
{
    const TEST = "test";

    public static function getConstants()
    {
        // "static::class" here does the magic
        $reflectionClass = new ReflectionClass(static::class);
        return $reflectionClass->getConstants();
    }
}

class ChildClass extends AbstractClass
{
    const TYPE_A = 1;
    const TYPE_B = 'hello';
}

$example = new ChildClass();
var_dump($example->getConstants());

// Result:
array(3) {
  'TYPE_A' => int(1)
  'TYPE_B' => string(5) "hello"
  'TEST' => string(4) "test"
}

?>

You can pass $this as class for the ReflectionClass. __CLASS__ won't help if you extend the original class, because it is a magic constant based on the file itself.

<?php 

class Example {
  const TYPE_A = 1;
  const TYPE_B = 'hello';

  public function getConstants()
  {
    $reflectionClass = new ReflectionClass($this);
    return $reflectionClass->getConstants();
  }
}

$example = new Example();
var_dump($example->getConstants());

// Result:
array ( size = 2)
  'TYPE_A' => int 1
  'TYPE_B' => (string) 'hello'

I use a functions to do somthing base on the class constant name as below. This example maybe helpful for everybody.
<?php
public function renderData($question_type = NULL, $data = array()) {
        $types = array();
        $qt = new ReflectionClass(questionType);
        $types = $qt->getConstants();
        if ($type = array_search($question_type, $types)){
                //.....Do somthing
}
}
?>

I was trying to determine how to get a var_dump of constants that are within an interface.  Thats right, not using any classes but the interface itself.

Along my travels I found it quite interesting that the ReflectionClass along with a direct call to the interface will also dump its constants.  Perfect!!!!

This was using PHP 5.3.1 and my example as below:-

1st File:

constants.php

<?php
<?php>

interface MyConstants
{
    // --------------------------
    // Programmatic Level
    // --------------------------
    const DEBUG_MODE_ACTIVE       = FALSE;
    const PHP_VERSION_REQUIREMENT = "5.1.2";
}
?>

=======
Second file:
=======

test.php

<?php>
include_once ("constants.php");

$oClass = new ReflectionClass ('MyConstants');
$array = $oClass->getConstants ();
var_dump ($array);
unset ($oClass);
?>

what you would get from the command line:-

?:\???\htdocs\????>php test.php
array(2) {
  ["DEBUG_MODE_ACTIVE"]=> bool(false)
  ["PHP_VERSION_REQUIREMENT"]=> string(5) "5.1.2"

But as you can see this can work quite well to your advantage in many ways so I truely hope this helps someone else with a similar headache in the future to come!

Enjoy!

Get the latest constants declared.

abstract class AbstractEnum
{
    /**
     * Возвращает все константы класса || Return all constants
     *
     * @return array
     */
    static function getConstants()
    {
        $rc = new \ReflectionClass(get_called_class());

        return $rc->getConstants();
    }

    /**
     * Возвращает массив констант определенные в вызываемом классе  || Return last constants
     *
     * @return array
     */
    static function lastConstants()
    {
        $parentConstants = static::getParentConstants();

        $allConstants = static::getConstants();

        return array_diff($allConstants, $parentConstants);
    }

    /**
     * Возвращает все константы родительских классов || Return parent constants
     *
     * @return array
     */
    static function getParentConstants()
    {
        $rc = new \ReflectionClass(get_parent_class(static::class));
        $consts = $rc->getConstants();

        return $consts;
    }
}

======
class Roles extends AbstractEnum
{
    const ROOT = 'root';
    const ADMIN = 'admin';
    const USER = 'user';
}

// Output:
All: root, admin, user 
Last: root, admin, user 

class NewRoles extends Roles
{
    const CLIENT = 'client';
    const MODERATOR = 'moderator';
    const SUPERMODERATOR = 'super'.self::USER;
}

// Output:
All: client, moderator, superuser, root, admin, user 
Last: client, moderator, superuser 

class AdditionalRoles extends Roles
{
    const VIEWER = 'viewer';
    const CHECKER = 'checker';
    const ROOT = 'rooter';
}

All: viewer, checker, rooter, client, moderator, superuser, admin, user 
Last: viewer, checker, rooter