composer: more information (#4111)

Co-authored-by: Zlatan Vasović <zlatanvasovic@gmail.com>

pages/common/composer.md

@@ -3,11 +3,15 @@
 > A package-based dependency manager for PHP projects.
 > More information: <https://getcomposer.org/>.
 
+- Interactively create a `composer.json` file:
+
+`composer init`
+
 - Add a package as a dependency for this project, adding it to `composer.json`:
 
 `composer require {{user/package_name}}`
 
-- Install all the dependencies in this project's `composer.json`:
+- Install all the dependencies in this project's `composer.json` and create `composer.lock`:
 
 `composer install`
 
@@ -15,10 +19,18 @@
 
 `composer remove {{user/package_name}}`
 
-- Update all the dependencies in this project's `composer.json`:
+- Update all the dependencies in this project's `composer.json` and note versions in `composer.lock` file:
 
 `composer update`
 
-- Update composer to the latest version:
+- Update composer lock only after updating `composer.json` manually:
+
+`composer update --lock`
+
+- Learn more about why a dependency can't be installed:
+
+`composer why-not {{user/package_name}}`
+
+- Update composer to its latest version:
 
 `composer self-update`