add supported versions page (#8238)

Author: LordSimal

docs/en/intro.md

@@ -162,3 +162,4 @@ The next obvious steps are to [download CakePHP](installation), read the
 - [Where to Get Help](intro/where-to-get-help)
 - [CakePHP Conventions](intro/conventions)
 - [CakePHP Folder Structure](intro/cakephp-folder-structure)
+- [Supported Versions](intro/supported-versions)

docs/en/intro/supported-versions.md

@@ -0,0 +1,46 @@
+# Semantic Versioning
+
+See [CakePHP Development Process](../appendices/cakephp-development-process.md) and the [Backwards Compatibility Guide](../contributing/backwards-compatibility)
+
+## CakePHP Supported Versions
+
+This table was last updated in February 2026.
+
+| Major Version | Supported Version | PHP-Version    | Active Support | Security Support     |
+|---------------|-------------------|----------------|----------------|----------------------|
+| `5.x`         | `5.1` to `5.3`    | `8.1` to `8.5` | `5.3+`         | ✅                    |
+| `4.x`         | `4.4` to `4.6`    | `7.2` to `8.3` | ❌              | September 10th, 2026 |
+| `3.x`         | None              | `5.6` to `7.4` | ❌              | ❌                    |
+| `2.x`         | None              | `5.4` to `7.4` | ❌              | ❌                    |
+| `1.x`         | None              | `¯\_(ツ)_/¯`    | ❌              | ❌                    |
+
+### Major Version Support
+
+We follow the rule to support the previous major version for
+- 24 months of `active support` (includes new features and bugfixes) and
+- 36 months of `security support`
+after the release of a new major version.
+
+E.g. [CakePHP 5.0](https://github.com/cakephp/cakephp/releases/tag/5.0.0) released on September 10th 2023,
+so we will support CakePHP 4.x until September 10th 2025 and provide security updates until September 10th 2026.
+
+### Minor Version Support
+
+`Active support` for a minor branch ends the moment a new minor branch is released.
+E.g. when CakePHP 4.2 is released, active support for CakePHP 4.1 will end and only security updates will be provided.
+
+`Security updates` will be provided
+- till the end of the support period for the major version, or
+- 3 new minor releases have been published (e.g. `4.2` support ended when `4.5` was released)
+
+whichever comes first.
+
+> [!TIP]
+> Keep production applications on a currently supported major line and plan
+> regular upgrades to stay within supported minor ranges.
+
+> [!TIP]
+> Each minor and major release of CakePHP includes automated upgrade commands which you
+> can use to upgrade your application or plugin. See e.g. the
+> [upgrade guide](../appendices/4-0-upgrade-guide.md#use-the-upgrade-tool)
+> for more details on how to use these commands.

toc_en.json

@@ -24,6 +24,10 @@
           "text": "CakePHP Folder Structure",
           "link": "/intro/cakephp-folder-structure"
         },
+        {
+          "text": "Supported Versions",
+          "link": "/intro/supported-versions"
+        },
         {
           "text": "Where to Get Help",
           "link": "/intro/where-to-get-help"