Generate legacy arginfo for older PHP versions (#1981)

* Add legacy arginfo directive for stub generator

* Update arginfo guidance in contributing docs

* Use latest PHP version to generate arginfo

* Update CONTRIBUTING.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update gen_stub instructions for coding agents

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: alcaeus

.claude/CLAUDE.md

@@ -60,7 +60,7 @@ PHP method signatures are defined in `*.stub.php` files alongside each class's `
 ./build/gen_stub.php
 ```
 
-This requires `phpize` to have been run with **PHP 8.2** to use all features. Commit both the stub and the generated arginfo file.
+This requires `phpize` to have been run with the latest stable PHP version to use all features. Commit both the stub and the generated arginfo file.
 
 ## Architecture
 

.github/workflows/arginfo-files.yml

@@ -11,7 +11,7 @@ on:
       - "feature/*"
 
 env:
-  PHP_VERSION: "8.2"
+  PHP_VERSION: "8.5"
 
 jobs:
   check-arginfo:

CONTRIBUTING.md

@@ -31,9 +31,14 @@ $ php --ri mongodb
 ## Generating arginfo from stub files
 
 Arginfo structures are generated from stub files using the `gen_stub.php`
-file. Note that this requires `phpize` to be run for **PHP 8.2** to make use
-of all features. After changing a stub file, run `./build/gen_stub.php`
-to regenerate the corresponding arginfo files and commit the results.
+file. After changing a stub file, run `./build/gen_stub.php` to regenerate the
+corresponding arginfo files and commit the results.
+
+The `gen_stub.php` file is added to the `build` directory when calling `phpize`.
+Arginfo structures are generated with the latest version of PHP. The
+`@generate-legacy-arginfo` directive ensures that the generated files are
+compatible with the indicated version of PHP. When bumping the minimum PHP
+requirement, this directive needs to be updated accordingly.
 
 ## Generating function maps for static analysis tools
 

src/BSON/Binary.stub.php

@@ -2,7 +2,7 @@
 
 /**
  * @generate-class-entries static
- * @generate-function-entries static
+ * @generate-legacy-arginfo 80100
  */
 
 namespace MongoDB\BSON;

src/BSON/BinaryInterface.stub.php

@@ -1,8 +1,8 @@
 <?php
 
 /**
- * @generate-class-entries static
- * @generate-function-entries
+ * @generate-class-entries
+ * @generate-legacy-arginfo 80100
  */
 
 namespace MongoDB\BSON;

src/BSON/BinaryInterface_arginfo.h

@@ -2,7 +2,7 @@
 
 /**
  * @generate-class-entries static
- * @generate-function-entries static
+ * @generate-legacy-arginfo 80100
  */
 
 namespace MongoDB\BSON;

src/BSON/Binary_arginfo.h

@@ -2,7 +2,7 @@
 
 /**
  * @generate-class-entries static
- * @generate-function-entries static
+ * @generate-legacy-arginfo 80100
  */
 
 namespace MongoDB\BSON;