[fw-general] Accessing class methods dynamically

[Simon R Jones]

I'm working on Zend_Validate_Hostname and have a need to access a method
within a class to get TLD specific regular expression characters. I don't
know the exact class name since it depends on the TLD in the hostname. 

In Zend_Validate_Hostname::isValid() it works like so:

$className = 'Zend_Validate_Hostname_' . ucfirst($valueTld);
Zend::loadClass($className);
$obj = new $className;
$labelChars .= $obj->getCharacters();


With the class specifying the characters looking something like this:

class Zend_Validate_Hostname_De implements Zend_Validate_Hostname_Interface 
{
    public function getCharacters()
    {
        return  '\x{00E1}...\x{00FE}';
    }
}


I have no need to actually instantiate the class object, but I cannot see
any other way to access the getCharacters() method. Ideally I'd just do:

Zend::loadClass($className);
$labelChars .= $className::getCharacters();


But variable variables and classes doesn't work in PHP.

Any bright ideas on a better way to access the getCharacters() method. Or is
my current approach fine?

best wishes,
Si