告别硬编码！如何使用Composer和dflydev/placeholder-resolver优雅地管理复杂配置

composer require dflydev/placeholder-resolver

<?php

require 'vendor/autoload.php';

use Dflydev\PlaceholderResolver\RegexPlaceholderResolver;
use Dflydev\PlaceholderResolver\DataSource\ArrayDataSource; // 假设你有一个数组数据源

// 你的配置数据源，可以是数组、文件、环境变量等
$configData = [
    'conn.driver' => 'mysql',
    'conn.db_name' => 'example_db',
    'conn.hostname' => '127.0.0.1',
    'conn.username' => 'root',
    'conn.password' => 'pa$$word',
    // 甚至可以有嵌套的占位符
    'base.url' => 'http://${conn.hostname}/api',
    'api.version' => 'v1',
    'full.api.endpoint' => '${base.url}/${api.version}/users',
    'foo' => 'BASE',
    'bar' => 'URL',
    'BASE.URL' => 'https://secure.example.com', // 用于递归解析
];

// 将配置数据包装成数据源接口的实现
// ArrayDataSource 是 dflydev/placeholder-resolver 提供的一个简单实现
$dataSource = new ArrayDataSource($configData);

// 创建占位符解析器
// RegexPlaceholderResolver 是一个基于正则表达式的解析器，默认占位符前缀是 `${`，后缀是 `}`
$placeholderResolver = new RegexPlaceholderResolver($dataSource);

// 示例1: 解析数据库 DSN
$dsnPattern = '${conn.driver}:dbname=${conn.db_name};host=${conn.hostname}';
$dsn = $placeholderResolver->resolveValue($dsnPattern);
echo "解析后的 DSN: " . $dsn . "\n";
// 预期输出: mysql:dbname=example_db;host=127.0.0.1

echo "--------------------\n";

// 示例2: 解析单个占位符
$username = $placeholderResolver->resolvePlaceholder('${conn.username}');
echo "解析后的用户名: " . $username . "\n";
// 预期输出: root

echo "--------------------\n";

// 示例3: 递归解析 - 占位符的值本身也包含占位符
// 这里 'full.api.endpoint' 的值是 '${base.url}/${api.version}/users'
// 而 'base.url' 的值是 'http://${conn.hostname}/api'
$apiEndpoint = $placeholderResolver->resolveValue('${full.api.endpoint}');
echo "递归解析的 API 端点: " . $apiEndpoint . "\n";
// 预期输出: http://127.0.0.1/api/v1/users

echo "--------------------\n";

// 示例4: 更复杂的递归解析 - 占位符的键名本身也是占位符
$complexRecursivePattern = '${${foo}.${bar}}'; // 内部先解析成 '${BASE.URL}'
$resolvedComplexRecursive = $placeholderResolver->resolveValue($complexRecursivePattern);
echo "更复杂的递归解析结果: " . $resolvedComplexRecursive . "\n";
// 预期输出: https://secure.example.com