composer require yiisoft/yii2-bootstrap4
Yii2 – Upgrading to Bootstrap 4
Please following the following steps to install Bootstrap 4 and uninstall old version of Boostrap.
Make sure you are in the Project Directory.
//-- If this line doesn't work: --/ composer require yiisoft/yii2-bootstrap4 //-- Then use the following command: --/ composer require --prefer-dist yiisoft/yii2-bootstrap4 And to remove old one run the following: composer remove yiisoft/yii2-bootstrap