public_producer/app/Tools/PinyinHelper.php

<?php
declare(strict_types=1);

namespace App\Tools;

use Overtrue\Pinyin\Pinyin;

class PinyinHelper
{
    public static function getFirstLetter(string $string): string
    {
        $pinyin = new Pinyin();
        return strtolower(implode('', $pinyin->abbr($string)->toArray()));
    }
}