src/Client.php
public function modifyRelationship($action, $user) {
        if (true === in_array($action, $this->_actions) && isset($user)) {
            return $this->_makeCall('users/' . $user . '/relationship', array('action' => $action), 'POST');
        }
        throw new InvalidParameterException('Error: modifyRelationship() - This method requires an action command and the target user id.');
    }
public function modifyRelationship($action, $user) {
        if (true === in_array($action, $this->_actions) && isset($user)) {
            return $this->_makeCall('users/' . $user . '/relationship', array('action' => $action), 'POST');
        }
        throw new InvalidParameterException('Error: modifyRelationship() - This method requires an action command and the target user id.');
    }
Modify the relationship between the current user and the target user

@param string $action                Action command (follow/unfollow/block/unblock/approve/deny)
@param integer $user                 Target user ID
@return mixed