Access substring of class constant with array index operator

Question

class Foo {
 const BAR = 'Hello';
}

echo Foo::BAR; //Works
echo Foo::BAR[0]; //Parse error: syntax error, unexpected '[', expecting ',' or ';'

I've found a way around this by using substr, but I'm curious to know why this doesn't work as it is.

PHP 5.3.3 by the way.

Answer 1

I guess that PHP considers class constants like "classic" constants (e.g. created with define()).

Therefore, they are simply replaced by their values at runtime, so Foo::BAR[0] would be interpreted by PHP as 'Hello'[0] which is not a valid syntax ($myVariable[0] being allowed).