Can I use string concatenation to define a class CONST in PHP?

Question

I know that you can create global constants in terms of each other using string concatenation:

define('FOO', 'foo');
define('BAR', FOO.'bar');  
echo BAR;

will print 'foobar'.

However, I'm getting an error trying to do the same using class constants.

class foobar {
  const foo = 'foo';
  const foo2 = self::foo;
  const bar = self::foo.'bar';
}

foo2 is defined without issue, but declaring const bar will error out

Parse error: syntax error, unexpected '.', expecting ',' or ';'

I've also tried using functions like sprintf() but it doesn't like the left paren any more than the string concatenator '.'.

So is there any way to create class constants in terms of each other in anything more than a trivial set case like foo2?

Answer 1

no.

(I don't think there is)

Answer 2

Always fall back to the trusty manual for stuff like this.

Regarding constants:

The value must be a constant expression, not (for example) a variable, a property, a result of a mathematical operation, or a function call.

So... "no" would be the answer :D

Answer 3

For class constants, you can't assign anything other than a constant expression. Quoting the PHP 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. "

Answer 4

The only way is to define() an expression and then use that constant in the class

define('foobar', 'foo' . 'bar');

class Foo
{
    const blah = foobar;
}

echo Foo::blah;

Another option is to go to bugs.php.net and kindly ask them to fix this.