Advice about bootstrap file is not up to date

[garak]

This part of the docs http://symfony.com/doc/master/performance.html#use-bootstrap-files looks not up to date with latest changes made in this PR symfony/symfony-standard#1030

[teohhanhui]

I think the docs can also recommend removing https://github.com/symfony/symfony-standard/blob/v3.2.6/composer.json#L35 when using PHP >= 7.0, say, with this in composer.json:

{
    ...
    "require": {
        "php": ">=7.0.0",
        ...
    }
    ...
}

The related code blocks could also be removed from both app.php and app_dev.php.

Current issue status:

• Present in 2.7 (Requires PHP >=5.3.9). Advise: keep it.
• Present in 2.8 (Requires PHP >=5.3.9). Advise: keep it.
• Present in 3.0, 3.1 and 3.2 but are not maintained versions.
• Not present in 3.3 (Requires PHP ^5.5.9|>=7.0.8). Advise: add note about version lower than PHP 7.
• Not present in 3.4 (Requires PHP ^5.5.9|>=7.0.8). Advise: add note about version lower than PHP 7.
• Not present in 4.0 (Requires PHP ^7.1.3). Advise: don't change or add anything.

ping: @weaverryan @xabbuh @javiereguiluz

[xabbuh]

If I am not completely mistaken, we had changes during the last half year which more or less ignored legacy PHP versions like 5.3 and so on. To me, we could just bring the docs for 2.7 and 2.8 in line with the Symfony 3 docs.

[javiereguiluz]

Closing as fixed. 2.8 and 3.4 include the "bootstrap" section but with a big warning about PHP 7. Starting from 4.0, the "bootstrap" section no longer exists. Thanks!