code: public function getLoginUrl($scope = array(), $state = null) {
          $scope = $this->mergeScope($scope);
  
          $state = is_string($state) ? "&state={$state}" : '';
  
          return self::API_OAUTH_URL .
              '?client_id=' . $this->getApiKey() .
              '&redirect_uri=' . urlencode($this->getApiCallback()) .
              '&scope=' . implode('+', $scope) .
              '&response_type=code' .
              $state;
      }
docs: Generates the OAuth login URL
  
  @param array [optional] $scope       Requesting additional permissions
  @return string                       Instagram OAuth login URL