ReportsGenerator::export()

	public function export()
	{
		$hash    = $this->hasArg('hash')? $this->args['hash'] : md5(microtime());
		$exports = get_transient($hash) ?: [];
		$columns = apply_filters('bp_ld_sync/export_report_column', $this->columns(), $this, $this->args);
		$data = apply_filters('bp_ld_sync/export_report_data', $this->getData(), $this, $this->args);

    	foreach ($data as $result) {
    		$data = [];

    		foreach (array_keys($columns) as $key) {
    			$data[$key] = $result[$key];
    		}

    		$exports[] = $data;
    	}

		set_transient($hash, $exports, HOUR_IN_SECONDS);
		set_transient("{$hash}_info", [
			'filename' => 'learndash-report-export-group-' . $this->args['group'] . '.csv',
			'columns' => $columns
		], HOUR_IN_SECONDS);

		wp_send_json_success([
			'page'     => $this->args['start'] / $this->args['length'] + 1,
			'total'    => $this->pager['total_pages'],
			'has_more' => $this->pager['total_pages'] > $this->args['start'] / $this->args['length'] + 1,
			'url'      => add_query_arg([
				'hash'   => $hash,
				'action' => 'download_bp_ld_reports',
			], admin_url('admin-ajax.php')),
			'hash'     => $hash
		]);
	}