Improvements

[samdark]

No description provided.

[Copilot]

Pull Request Overview

This PR refines the documentation and examples across the guides by updating supported PHP versions, normalizing header casing and anchor IDs, and modernizing code examples with final readonly classes and constructor property promotion.

• Bump PHP requirement from 8.0 to 8.1 in multiple guides
• Standardize section headings (casing and anchor ids)
• Update code snippets to use final readonly classes and constructor property promotion
• Fix typos and placeholders (e.g., package names, links)

Reviewed Changes

Copilot reviewed 33 out of 33 changed files in this pull request and generated no comments.

File	Description
guide/ru/intro/what-is-yii.md	Bumped PHP requirement to 8.1
guide/en/intro/what-is-yii.md	Bumped PHP requirement to 8.1
guide/en/tutorial/using-with-event-loop.md	Added FrankenPHP mention (placeholder link) and updated state strategies
guide/en/tutorial/performance-tuning.md	Lowercased headings and updated anchor id attributes

Comments suppressed due to low confidence (2)

guide/en/tutorial/using-with-event-loop.md:12

• The link placeholder <LINK HERE> for FrankenPHP needs to be replaced with the actual URL to the FrankenPHP docs or repository.

There are multiple tools that could be used to achieve it. Notably, [FrankenPHP](<LINK HERE>), [RoadRunner](https://roadrunner.dev/) and

guide/en/tutorial/performance-tuning.md:19

• The anchor ID was changed from using-caching to using-caching-techniques; ensure any links or references elsewhere are updated to match the new ID.

## Using caching techniques <span id="using-caching-techniques"></span>