What is going on in page.php?

// Walk pairs of params adding search parameters
if (!empty($this->_params) && count($this->_params) % 2 == 0) {
	for ($i = 0; $i < count($this->_params); $i += 2) {
		switch ($this->_params[$i]) {
			case 'city':
				$city = $this->_params[$i + 1];
				break;
			case 'keywords':
				$keywords = $this->_params[$i + 1];
				break;
			case 'state':
				$state = $this->_params[$i + 1];
				break;

                    	default:
                        	$a = 1;
			}
		}
	}