feat(librarian/internal/config): add php config (#6701)

Add initial set of config for PHP.

For #6629

Author: zhumin8

doc/config-schema.md

@@ -135,6 +135,7 @@ This document describes the schema for the librarian.yaml.
 | `go` | [GoModule](#gomodule-configuration) (optional) | Contains Go-specific library configuration. |
 | `java` | [JavaModule](#javamodule-configuration) (optional) | Contains Java-specific library configuration. |
 | `nodejs` | [NodejsPackage](#nodejspackage-configuration) (optional) | Contains Node.js-specific library configuration. |
+| `php` | [PHPPackage](#phppackage-configuration) (optional) | Contains PHP-specific library configuration. |
 | `python` | [PythonPackage](#pythonpackage-configuration) (optional) | Contains Python-specific library configuration. |
 | `rust` | [RustCrate](#rustcrate-configuration) (optional) | Contains Rust-specific library configuration. |
 | `swift` | [SwiftPackage](#swiftpackage-configuration) (optional) | Contains Swift-specific library configuration. |
@@ -190,6 +191,7 @@ This document describes the schema for the librarian.yaml.
 | `go` | [GoAPI](#goapi-configuration) (optional) | Contains Go-specific API configuration. |
 | `java` | [JavaAPI](#javaapi-configuration) (optional) | Contains Java-specific API configuration. |
 | `nodejs` | [NodejsAPI](#nodejsapi-configuration) (optional) | Contains Node.js-specific API configuration. |
+| `php` | [PHPAPI](#phpapi-configuration) (optional) | Contains PHP-specific API configuration. |
 
 ## GoDefault Configuration
 
@@ -418,6 +420,17 @@ This document describes the schema for the librarian.yaml.
 | `metadata_name_override` | string | Allows the name field in .repo-metadata.json to be overridden. |
 | `name_pretty_override` | string | Allows the name_pretty field in .repo-metadata.json to be overridden. |
 
+## PHPAPI Configuration
+
+| Field | Type | Description |
+| :--- | :--- | :--- |
+| `migration_mode` | string | Controls migration mode setting for the PHP generator (e.g. "NEW_SURFACE_ONLY"). |
+
+## PHPPackage Configuration
+
+| Field | Type | Description |
+| :--- | :--- | :--- |
+
 ## PythonDefault Configuration
 
 | Field | Type | Description |

internal/config/config.go

@@ -330,6 +330,9 @@ type Library struct {
 	// Nodejs contains Node.js-specific library configuration.
 	Nodejs *NodejsPackage `yaml:"nodejs,omitempty"`
 
+	// PHP contains PHP-specific library configuration.
+	PHP *PHPPackage `yaml:"php,omitempty"`
+
 	// Python contains Python-specific library configuration.
 	Python *PythonPackage `yaml:"python,omitempty"`
 
@@ -423,6 +426,9 @@ type API struct {
 
 	// Nodejs contains Node.js-specific API configuration.
 	Nodejs *NodejsAPI `yaml:"nodejs,omitempty"`
+
+	// PHP contains PHP-specific API configuration.
+	PHP *PHPAPI `yaml:"php,omitempty"`
 }
 
 // GoDefault defines Go-specific default configuration.

internal/config/language.go

@@ -804,3 +804,13 @@ type NodejsAPI struct {
 	// Path is the source path.
 	Path string `yaml:"path,omitempty"`
 }
+
+// PHPPackage contains PHP-specific library configuration.
+type PHPPackage struct {
+}
+
+// PHPAPI represents configuration for a single API within a PHP package.
+type PHPAPI struct {
+	// MigrationMode controls migration mode setting for the PHP generator (e.g. "NEW_SURFACE_ONLY").
+	MigrationMode string `yaml:"migration_mode,omitempty"`
+}