Composer always installs Symfony 3.4 and not the latest 4 version?

Question

symfony

Good day. Recently I started getting acquainted with Symfony, found a tutorial and started learning. The lessons were about Symfony 3.4 Installed by composer with version indication. Now I decided to look at Symfony 4. I also install the composer without specifying the version (in theory) should I install the latest stable, i.e. 4, but stubbornly put 3.4.6? , / I don't understand why this is happening? Already cleared the compiler cache. all the same

Answer 1

If composer is launched using a PHP version lower than 7.1.3, then the latest supported version of Symfony by this PHP version, i.e. 3.4.6, is installed, if the PHP version is higher or equal to the minimum requirements, then Symfony 4 is installed accordingly.
Also in the documentation for the third version it is indicated that the symfony/framework-standard-edition package is used for installation, but in the README it is written that the Symfony version in it will no longer be higher than 3, and you must install either symfony/website-skeleton or symfony/skeleton