Not clear how define('YII_ENV', 'dev') creates the YII_ENV_DEV
constant. Seems like an odd bit of magic that may confuse others…

Should it be “quality of these articles may not be as good”?

Spanish guide structure-application-components.md [skip ci]

Application templates refactoring

[ci skip]

intro upgrade from v1 guide translated

Create caching-page.md

French start-installation.md

Fix typo in start-installation.md

fixes #3891

Translation es

English guide small fix [skip ci]

Translate "Page Caching"

docs about file validator fixed

Spanish guide polish and start-looking-head.md [skip ci]