Yoda Condition

<?php
class Foo
{
	const BAR = 'Hallo';
	const BAZ = 'Welt!';

	/**
	 * 
	 * Returns the value of a class constant
	 * @param string $const Name of the constant
	 * @param string $class [optional] Name of the class (if not set, the constant will be searched in this class) 
	 * @return mixed|false The value of the constant or false if it does not exists
	 */
	public static function get_constant( $const = '', $class_name = __CLASS__ ){

		if( empty( $const ) || ! is_string( $const ) || ! class_exists( $class_name ) )
			return FALSE;

		$reflection = new ReflectionClass( $class_name );

		return $reflection->getConstant( $const );

	}

}

class Bar
{
	const FOO = 'Horst';
}

$consts = array( 'BAR', 'BAZ', 'FOO' );
foreach( $consts as $const )
	var_dump( Foo::get_constant( $const ) );

var_dump( Foo::get_constant( 'FOO', 'Bar' ) );

var_dump( Foo::get_constant( 'TEST', 'Baz' ) );