Idea for PHP typesafe enum

TypesafeEnum.php

<?php

/**
 * To create some typesafe enums, just extend this class, declare some static
 * properties, then call YourClassName::setUp(). Example follows.
 *
 * Disadvantages:
 *   - Since the enums are public properties, they could be modified by
 *     mistake (or intentionally by malicious code).
 *   - YourClassName::setUp() must be called.
 *   - $ required in front of enum name.
 *
 * Advantages:
 *   - IDE autocompletion should work.
 */
abstract class TypesafeEnum {

	private $name;

	public static function setUp() {
		$calledClassName = get_called_class();
		$calledClass = new ReflectionClass( $calledClassName );

		$props = $calledClass->getProperties( ReflectionProperty::IS_STATIC );

		foreach ( $props as $prop ) {
			$prop->setValue( new $calledClassName( $prop->getName() ) );
		}
	}

	private function __construct( $name ) {
		$this->name = $name;
	}

	public function __toString() {
		return $this->name;
	}
}

// Example use
final class MyHappyEnum extends TypesafeEnum {

	// Don't initialize these, just declare them.
	static $ENUM_ONE;
	static $ENUM_TWO;
	static $ENUM_THREE;
}

// Gotta call this somewhere, but only once. Could put it in the same file as
// the concrete class, I think.
MyHappyEnum::setUp();

// Here's the function we'll use to demonstrate
$func = function( MyHappyEnum $enum ) {

	// Got the right class
	print 'Class of parameter is ' . get_class( $enum ) . "\n";

	// __toString() works
	print 'Name is ' . $enum . "\n";

	// Switch also works normally
	switch ( $enum ) {

		case MyHappyEnum::$ENUM_ONE:
			print "Switch: one\n";
			break;

		case MyHappyEnum::$ENUM_TWO:
			print "Switch: two\n";
			break;

		case MyHappyEnum::$ENUM_THREE:
			print "Switch: three\n";
			break;

		default:
			throw new Exception( "Shouldn't happen." );
	}
};

print ( "Testing call with " . MyHappyEnum::$ENUM_TWO . "\n\n" );
$func( MyHappyEnum::$ENUM_TWO );

print ( "\n\nTesting call with " . MyHappyEnum::$ENUM_THREE . "\n\n" );
$func( MyHappyEnum::$ENUM_THREE );

// All of these cause a fatal error. Uncomment any one to try it.
// $func( new MyHappyEnum( 'Can\'t instantiate anywhere else.' ) );
// $func( 'Type hint prevents passing anything else.' );
// $func( MyHappyEnum::$CAN_T_USE_NON_EXISTENT_ENUM );

Compare with https://gist.github.com/AndrewGreen/9866433