isset on static class attributes

Question

class A {
    public static $foo = 42;
}

$class = 'A';
$attribute = 'foo';

var_dump(isset($class::$attribute)); //gives bool(false)

How can i checkt, of this static attribute exists in this class?

Podite

Please stop writing tags in question titles. – Catricecatrina

@Tomala Geret'kal: ok, next time i'll do it right :) – Podite

Answer 1

Use variable variables:

var_dump(isset($class::$$attribute)); // the two dollars are intentional

If you don't have PHP 5.3 yet the only accurate way is probably using the Reflection API:

$reflectionClass = new ReflectionClass($class);
$exists = $reflectionClass->hasProperty($attribute) && $reflectionClass->getProperty($attribute)->isStatic();

Dnieper

Thanks, that works :) I accept you answer as soon as I can (12 minutes left) :) – Podite

Wow, variable variables can get confusing quick. – Foggy

@JohnP: Probably you are using an older PHP version. The $class:: syntax was introduced in PHP 5.3. – Dnieper

@nikic: How can i do this for PHP < 5.3? I want have as much compability to older versions as possible. – Podite

@nikic ahhh, that's it. I haven't migrated to 5.3 yet. Was just about to -1 you after running it on codepad to verify. Apparently they haven't migrated yet either ^_^ – Neutralize

I'm still waiting for 5.4 when you can also write $$class::$$attribute. – Wilen

I think that property_exists($class, $attribute) is clearer, though it won't distinguish between static and non-static members, and it only works on non-public members as of 5.3. – Catricecatrina

@mario: Just checked trunk and the part before T_PAAMAYIM_NEKUDOTAYIM is still only class_name or reference_variable. $$class would need at least a variable_without_objects ;) – Dnieper

get_class_vars might be useful. – Catricecatrina

@levu: I added a possibility using Reflection ;) – Dnieper

Answer 2

In 5.3, you can simply do

var_dump(property_exists($class, $attribute));

Muniments

property_exists('class','attribute') to clarify this answer – Momentary