如何访问CakePHP Shell参数？

I am working on a cake shell script. When I use some named arguments eg:

--username=world

how can I get the "username" param / value?

My code looks like this:

class InviteShell extends AppShell
{
//... here are my methods.

public function getOptionParser()
    {
        $parser = parent::getOptionParser();
        $parser->addArgument('username', array(
            'help' => 'Send E-Mail to which user?'
        ))->addOption('method', array(
            'short' => 'm',
            'help' => __('The specific method you want help on.')
        ))->description(__('Lookup doc block comments for classes in CakePHP'));
        return $parser;
    }

}

And what is the difference between argument and option? And also how can I read these options in my code?

The one thing that works is I can read the $this->args array, but this is not named. All I can do is get the arg by index, eg.: $this->args[0]

I am using Cake 2.9

Arguments are positional values, options are prefixed values:

shell_method argument1 argument2 --optionA=value --optionB=value

So in your case username is a positional argument that will be looked up at position 0, and method is a prefix option that can occour anywhere.

shell_method userA --method=methodX
shell_method --method=methodX userA

In both cases the userA value will be available in $this->args[0], and the methodX value will be available in $this->params['method'] or via $this->param('method').