Description:
------------
We have to work around certain unnecessary limitations regarding class constants.
See 'Test script' for complete details on what bothers me (and other PHP 
developers)

Test script:
---------------
// Example 1: valid
const IMAGE_ROOT = '/www/public/img';

// Example 2: valid
define ('PUBLIC_ROOT', '/www/public');
define ('IMAGE_ROOT', PUBLIC_ROOT . '/img');
const FOO = IMAGE_ROOT;

// Example 3: invalid
define ('PUBLIC_ROOT', '/www/public');
const IMAGE_ROOT = PUBLIC_ROOT . '/img';

According to the manual:
"The value must be a constant expression, not (for example) a variable,
a property, a result of a mathematical operation, or a function call."

My question is: why is the concatenation of one or more CONSTANT values
prohibited in PHP? It doesn't have any added value, and even worse: makes
source code less readable because we have to clutter it with defined named constants or replace them with static properties as means of a workaround.