JsonSchema using Validation rule at Laravel 5.8

JsonSchemaRule.php

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;
use JsonSchema\Validator;


/**
 * Class JsonSchemaRule
 * @package App\Rules
 *
 * スキーマは https://jsonschema.net/ で作っている
 *
 * example:
 *   new JsonSchemaRule('post_request_schema.json'),
 */
class JsonSchemaRule implements Rule
{
    /**
     * @var string
     */
    protected $schema_file;

    /**
     * @var
     */
    protected $errors;

    /**
     * JsonSchemaRule constructor.
     * @param string $schema_file
     * @throws \Illuminate\Contracts\Filesystem\FileNotFoundException
     */
    public function __construct(string $schema_file)
    {
        $this->schema_file = $file_path;
        if (\File::exists( $this->schema_file ) === false) {
            throw new \RuntimeException( 'Not Found json schema file: ' . $this->schema_file );
        }
    }

    /**
     * Determine if the validation rule passes.
     *
     * @param string $attribute
     * @param mixed $value
     * @return bool
     */
    public function passes($attribute, $value)
    {
        $validator = new Validator();
        $data = \GuzzleHttp\json_decode( $value );

        $validator->validate(
            $data,
            (object)[ '$ref' => 'file://' . $this->schema_file ]
        );

        if ($validator->isValid()) {
            return true;
        }

        $this->errors = $validator->getErrors();
        \Log::info($this->errors);
        return false;
    }

    /**
     * Get the validation error message.
     *
     * @return string
     */
    public function message()
    {
        return 'json unvalid.';
    }
}