docs: update extension generator doc for a more natural order (#2279)

I've been advised during Dutch PHP Conference (thanks @dseguy!) to move
the "Generate your extension" section before going deep into type
juggling. I agree: the reader will have way more satisfaction and will
be eager to dig the topic if the basic case already works.

There may be more to improve but this is a first quick-win.

Author: alexandre-daubois

docs/extensions.md

@@ -80,7 +80,65 @@ There are two important things to note here:
 - A directive comment `//export_php:function` defines the function signature in PHP. This is how the generator knows how to generate the PHP function with the right parameters and return type;
 - The function must return an `unsafe.Pointer`. FrankenPHP provides an API to help you with type juggling between C and Go.
 
-While the first point speaks for itself, the second may be harder to apprehend. Let's take a deeper dive to type juggling in the next section.
+While the first point speaks for itself, the second may be harder to apprehend. Let's take a deeper dive to type juggling later in this guide.
+
+### Generating the Extension
+
+This is where the magic happens, and your extension can now be generated. You can run the generator with the following command:
+
+```console
+GEN_STUB_SCRIPT=php-src/build/gen_stub.php frankenphp extension-init my_extension.go
+```
+
+> [!NOTE]
+> Don't forget to set the `GEN_STUB_SCRIPT` environment variable to the path of the `gen_stub.php` file in the PHP sources you downloaded earlier. This is the same `gen_stub.php` script mentioned in the manual implementation section.
+
+If everything went well, your project directory should contain the following files for your extension:
+
+- **`my_extension.go`** - Your original source file (remains unchanged)
+- **`my_extension_generated.go`** - Generated file with CGO wrappers that call your functions
+- **`my_extension.stub.php`** - PHP stub file for IDE autocompletion
+- **`my_extension_arginfo.h`** - PHP argument information
+- **`my_extension.h`** - C header file
+- **`my_extension.c`** - C implementation file
+- **`README.md`** - Documentation
+
+> [!IMPORTANT]
+> **Your source file (`my_extension.go`) is never modified.** The generator creates a separate `_generated.go` file containing CGO wrappers that call your original functions. This means you can safely version control your source file without worrying about generated code polluting it.
+
+### Integrating the Generated Extension into FrankenPHP
+
+Our extension is now ready to be compiled and integrated into FrankenPHP. To do this, refer to the FrankenPHP [compilation documentation](compile.md) to learn how to compile FrankenPHP. Add the module using the `--with` flag, pointing to the path of your module:
+
+```console
+CGO_ENABLED=1 \
+XCADDY_GO_BUILD_FLAGS="-ldflags='-w -s' -tags=nobadger,nomysql,nopgx" \
+CGO_CFLAGS=$(php-config --includes) \
+CGO_LDFLAGS="$(php-config --ldflags) $(php-config --libs)" \
+xcaddy build \
+    --output frankenphp \
+    --with github.com/my-account/my-module/build
+```
+
+Note that you point to the `/build` subdirectory that was created during the generation step. However, this is not mandatory: you can also copy the generated files to your module directory and point to it directly.
+
+### Testing Your Generated Extension
+
+You can create a PHP file to test the functions and classes you've created. For example, create an `index.php` file with the following content:
+
+```php
+<?php
+
+// Using global constants
+var_dump(repeat_this('Hello World', 5, STR_REVERSE));
+
+// Using class constants
+$processor = new StringProcessor();
+echo $processor->process('Hello World', StringProcessor::MODE_LOWERCASE);  // "hello world"
+echo $processor->process('Hello World', StringProcessor::MODE_UPPERCASE);  // "HELLO WORLD"
+```
+
+Once you've integrated your extension into FrankenPHP as demonstrated in the previous section, you can run this test file using `./frankenphp php-server`, and you should see your extension working.
 
 ### Type Juggling
 
@@ -580,64 +638,6 @@ echo My\Extension\STATUS_ACTIVE; // 1
 - Namespace names follow PHP namespace conventions using backslashes (`\`) as separators.
 - If no namespace is declared, symbols are exported to the global namespace as usual.
 
-### Generating the Extension
-
-This is where the magic happens, and your extension can now be generated. You can run the generator with the following command:
-
-```console
-GEN_STUB_SCRIPT=php-src/build/gen_stub.php frankenphp extension-init my_extension.go
-```
-
-> [!NOTE]
-> Don't forget to set the `GEN_STUB_SCRIPT` environment variable to the path of the `gen_stub.php` file in the PHP sources you downloaded earlier. This is the same `gen_stub.php` script mentioned in the manual implementation section.
-
-If everything went well, your project directory should contain the following files for your extension:
-
-- **`my_extension.go`** - Your original source file (remains unchanged)
-- **`my_extension_generated.go`** - Generated file with CGO wrappers that call your functions
-- **`my_extension.stub.php`** - PHP stub file for IDE autocompletion
-- **`my_extension_arginfo.h`** - PHP argument information
-- **`my_extension.h`** - C header file
-- **`my_extension.c`** - C implementation file
-- **`README.md`** - Documentation
-
-> [!IMPORTANT]
-> **Your source file (`my_extension.go`) is never modified.** The generator creates a separate `_generated.go` file containing CGO wrappers that call your original functions. This means you can safely version control your source file without worrying about generated code polluting it.
-
-### Integrating the Generated Extension into FrankenPHP
-
-Our extension is now ready to be compiled and integrated into FrankenPHP. To do this, refer to the FrankenPHP [compilation documentation](compile.md) to learn how to compile FrankenPHP. Add the module using the `--with` flag, pointing to the path of your module:
-
-```console
-CGO_ENABLED=1 \
-XCADDY_GO_BUILD_FLAGS="-ldflags='-w -s' -tags=nobadger,nomysql,nopgx" \
-CGO_CFLAGS=$(php-config --includes) \
-CGO_LDFLAGS="$(php-config --ldflags) $(php-config --libs)" \
-xcaddy build \
-    --output frankenphp \
-    --with github.com/my-account/my-module/build
-```
-
-Note that you point to the `/build` subdirectory that was created during the generation step. However, this is not mandatory: you can also copy the generated files to your module directory and point to it directly.
-
-### Testing Your Generated Extension
-
-You can create a PHP file to test the functions and classes you've created. For example, create an `index.php` file with the following content:
-
-```php
-<?php
-
-// Using global constants
-var_dump(repeat_this('Hello World', 5, STR_REVERSE));
-
-// Using class constants
-$processor = new StringProcessor();
-echo $processor->process('Hello World', StringProcessor::MODE_LOWERCASE);  // "hello world"
-echo $processor->process('Hello World', StringProcessor::MODE_UPPERCASE);  // "HELLO WORLD"
-```
-
-Once you've integrated your extension into FrankenPHP as demonstrated in the previous section, you can run this test file using `./frankenphp php-server`, and you should see your extension working.
-
 ## Manual Implementation
 
 If you want to understand how extensions work or need full control over your extension, you can write them manually. This approach gives you complete control but requires more boilerplate code.