php/app/validate/CommonValidate.php

<?php

namespace app\validate;

use think\facade\Request;
use think\Validate;

class CommonValidate extends Validate
{
    protected $request;

    public function __construct(Request $request)
    {
        $this->request = $request;
        parent::__construct();
    }

    // 自定义验证规则：验证是否为有效的JSON格式
    protected function isJson($value): bool
    {
        json_decode($value);
        return (json_last_error() == JSON_ERROR_NONE);
    }
}