如何在composer脚本中获取项目根目录等变量？

use Composer\Script\Event;
use Composer\Util\Filesystem;

class BuildScript
{
    public static function postInstall(Event $event)
    {
        $composer = $event->getComposer();
        // 获取项目根目录（即 composer.json 所在目录）
        $rootDir = $composer->getConfig()->get('vendor-dir') . '/..';
        $rootDir = realpath($rootDir);

        echo "项目根目录: " . $rootDir . PHP_EOL;

        // 其他常用路径
        $vendorDir = $composer->getConfig()->get('vendor-dir');     // vendor 目录
        $binDir    = $composer->getConfig()->get('bin-dir');        // bin 目录

        echo "Vendor 目录: " . $vendorDir . PHP_EOL;
        echo "Bin 目录: " . $binDir . PHP_EOL;
    }
}

public static function myScript(Event $event)
{
    // 方法1：推荐，可靠
    $root = getcwd();
    echo "根目录（getcwd）: " . $root . PHP_EOL;

    // 方法2：通过 vendor 推算
    $vendorDir = $event->getComposer()->getConfig()->get('vendor-dir');
    $root = realpath($vendorDir . '/..');

    echo "根目录（vendor 推算）: " . $root . PHP_EOL;
}

"scripts": {
    "post-install-cmd": "php scripts/build.php root=$(pwd)"
}