Check if a class constant exists

Question

How can I check if a constant is defined in a PHP class?

class Foo {
    const BAR = 1;
}

Is there something like property_exists()

Answer 1

You can use that function:

function constant_exists($class, $name){
    if(is_string($class)){
        return defined("$class::$name");
    } else if(is_object($class)){
        return defined(get_class($class)."::$name");
    }
    return false;
}

Or alternative version using ReflectionClass

function constant_exists($class, $name) {
    if(is_object($class) || is_string($class)){
        $reflect = new ReflectionClass($class);
        return array_key_exists($name, $reflect->getConstants());
    }
    return false;
}