Craft\AmForms_ExportsService::restartExport PHP Method

    public function restartExport(AmForms_ExportModel $export)
    {
        // Get the form
        $form = craft()->amForms_forms->getFormById($export->formId);
        if (!$form) {
            throw new Exception(Craft::t('No form exists with the ID “{id}”.', array('id' => $export->formId)));
        }
        // Delete old export
        if (IOHelper::fileExists($export->file)) {
            IOHelper::deleteFile($export->file);
        }
        // Reset finished
        $export->finished = false;
        if (!$export->submissions) {
            // Set total records to export
            $export->total = craft()->db->createCommand()->select('COUNT(*)')->from('amforms_submissions')->where('formId=:formId', array(':formId' => $export->formId))->queryScalar();
        }
        // Create a new export file
        $export->file = $this->_createExportFile($export, $form);
        // Save export and start export!
        if ($this->saveExport($export)) {
            // Start task
            $params = array('exportId' => $export->id, 'batchSize' => craft()->amForms_settings->getSettingsValueByHandleAndType('exportRowsPerSet', AmFormsModel::SettingExport, 100));
            craft()->tasks->createTask('AmForms_Export', Craft::t('{form} export', array('form' => $form->name)), $params);
            // Notify user
            craft()->userSession->setNotice(Craft::t('Export started.'));
        }
    }