Create book for docs

Closes phpGH-13338

.github/workflows/docs.yml

@@ -0,0 +1,29 @@
+name: Docs
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - docs/*
+  pull_request:
+    paths:
+      - docs/*
+jobs:
+  pages:
+    runs-on: ubuntu-22.04
+    permissions:
+      pages: write
+      id-token: write
+    steps:
+      - name: git checkout
+        uses: actions/checkout@v4
+      - name: Install dependencies
+        run: pip install sphinx-design sphinxawesome-theme rstfmt
+      - name: Check formatting
+        run: rstfmt --check -w 100 docs/source
+      - name: Publish
+        if: github.event_name == 'push'
+        uses: sphinx-notes/pages@v3
+        with:
+          checkout: false
+          documentation_path: docs/source

docs/.gitignore

@@ -0,0 +1 @@
+build/

docs/README.md

@@ -0,0 +1,31 @@
+# php-src docs
+
+This is the home of the php-src internal documentation. It is in very early stages, but is intended
+to become the primary place where new information about php-src is documented. Over time, it is
+expected to replace various mediums like:
+
+* https://www.phpinternalsbook.com/
+* https://wiki.php.net/internals
+* Blogs from contributors
+
+## How to build
+
+`python` 3 and `pip` are required.
+
+```bash
+pip install sphinx sphinx-design sphinxawesome-theme
+make html
+```
+
+That's it! You can view the documentation under `./build/html/index.html` in your browser.
+
+## Formatting
+
+The files in this documentation are formatted using the [``rstfmt``](https://github.com/dzhu/rstfmt) tool.
+
+```bash
+rstfmt -w 100 source
+```
+
+This tool is not perfect. It breaks on custom directives, so we might switch to either a fork or
+something else in the future.

docs/make.bat

@@ -0,0 +1,35 @@
+@ECHO OFF
+
+pushd %~dp0
+
+REM Command file for Sphinx documentation
+
+if "%SPHINXBUILD%" == "" (
+	set SPHINXBUILD=sphinx-build
+)
+set SOURCEDIR=source
+set BUILDDIR=build
+
+%SPHINXBUILD% >NUL 2>NUL
+if errorlevel 9009 (
+	echo.
+	echo.The 'sphinx-build' command was not found. Make sure you have Sphinx
+	echo.installed, then set the SPHINXBUILD environment variable to point
+	echo.to the full path of the 'sphinx-build' executable. Alternatively you
+	echo.may add the Sphinx directory to PATH.
+	echo.
+	echo.If you don't have Sphinx installed, grab it from
+	echo.https://www.sphinx-doc.org/
+	exit /b 1
+)
+
+if "%1" == "" goto help
+
+%SPHINXBUILD% -M %1 %SOURCEDIR% %BUILDDIR% %SPHINXOPTS% %O%
+goto end
+
+:help
+%SPHINXBUILD% -M help %SOURCEDIR% %BUILDDIR% %SPHINXOPTS% %O%
+
+:end
+popd

docs/source/conf.py

@@ -0,0 +1,59 @@
+# Configuration file for the Sphinx documentation builder.
+#
+# For the full list of built-in configuration values, see the documentation:
+# https://www.sphinx-doc.org/en/master/usage/configuration.html
+
+from dataclasses import asdict
+from sphinxawesome_theme import ThemeOptions
+from sphinxawesome_theme.postprocess import Icons
+from sphinx.highlighting import lexers
+from pygments.lexers.web import PhpLexer
+
+lexers['php'] = PhpLexer(startinline=True)
+lexers['php-annotations'] = PhpLexer(startinline=True)
+
+project = 'php-src docs'
+author = 'The PHP Group'
+extensions = [
+    'sphinx_design',
+    'sphinxawesome_theme.highlighting',
+]
+templates_path = ['_templates']
+html_theme = 'sphinxawesome_theme'
+html_static_path = ['_static']
+html_title = project
+html_permalinks_icon = Icons.permalinks_icon
+theme_options = ThemeOptions(
+    show_prev_next=True,
+    extra_header_link_icons={
+        'repository on GitHub': {
+            'link': 'https://github.com/php/php-src',
+            'icon': (
+                '<svg height="26px" style="margin-top:-2px;display:inline" '
+                'viewBox="0 0 45 44" '
+                'fill="currentColor" xmlns="http://www.w3.org/2000/svg">'
+                '<path fill-rule="evenodd" clip-rule="evenodd" '
+                'd="M22.477.927C10.485.927.76 10.65.76 22.647c0 9.596 6.223 17.736 '
+                '14.853 20.608 1.087.2 1.483-.47 1.483-1.047 '
+                '0-.516-.019-1.881-.03-3.693-6.04 '
+                '1.312-7.315-2.912-7.315-2.912-.988-2.51-2.412-3.178-2.412-3.178-1.972-1.346.149-1.32.149-1.32 '  # noqa
+                '2.18.154 3.327 2.24 3.327 2.24 1.937 3.318 5.084 2.36 6.321 '
+                '1.803.197-1.403.759-2.36 '
+                '1.379-2.903-4.823-.548-9.894-2.412-9.894-10.734 '
+                '0-2.37.847-4.31 2.236-5.828-.224-.55-.969-2.759.214-5.748 0 0 '
+                '1.822-.584 5.972 2.226 '
+                '1.732-.482 3.59-.722 5.437-.732 1.845.01 3.703.25 5.437.732 '
+                '4.147-2.81 5.967-2.226 '
+                '5.967-2.226 1.185 2.99.44 5.198.217 5.748 1.392 1.517 2.232 3.457 '
+                '2.232 5.828 0 '
+                '8.344-5.078 10.18-9.916 10.717.779.67 1.474 1.996 1.474 4.021 0 '
+                '2.904-.027 5.247-.027 '
+                '5.96 0 .58.392 1.256 1.493 1.044C37.981 40.375 44.2 32.24 44.2 '
+                '22.647c0-11.996-9.726-21.72-21.722-21.72" '
+                'fill="currentColor"/></svg>'
+            ),
+        },
+    },
+)
+html_theme_options = asdict(theme_options)
+pygments_style = 'sphinx'

docs/source/core/data-structures/index.rst

@@ -0,0 +1,12 @@
+#################
+ Data structures
+#################
+
+.. toctree::
+   :hidden:
+
+   zval
+   reference-counting
+   zend_string
+
+This section provides an overview of the core data structures used in php-src.