Trick to get options from default values.

defaults.php

<?php

class TestStuff {
	
	private $defaults = array(
		'color' => '#00ff00'
	);
	
	public function doIt() {
		return $this->__request(array('color' => '#ff0000'));
	}
	
	public function getIt() {
		return $this->__request();
	}
	
	private function __request(array $options = array()) {
		$options = array_filter(array_intersect_key(array_merge($this->defaults, $options), $this->defaults));
		echo $options; // from doIt it would echo '#ff0000' but from getIt it would be '#00ff00'
	}
}

function (array $options)
{
    $defaults = array(...);
    $options = $options + $defaults;
    return $options['key'];
}