To generate excel by query content, and download through any controller. You also can bind cssClass to header/odd/even rows. As for header, you even can set cssClass for each column.
$this->export2excel($excel_content,$excel_file);
in your controller.
This tutorial need extension mdmsoft/yii2-upload-file. Follow the intruction to install.
After installation done, create controller and action
You would find having such a need in most Yii Projects. Your database needs a specific format to store date fields, while you may want to display it in different formats to the users on forms and other views.
You have different collections in MongoDb with de-normalized attributes. As you may know, due to its not-join nature, MongoDb tends to encourage repetition of the same value in different collections (de-normalization). In this MongoDb is opposed to a more SQL-like approach where you usually reference only the ID of the value with a foreign key.