opnform/app/Rules/ValidPhoneInputRule.php

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;
use Illuminate\Support\Str;

class ValidPhoneInputRule implements Rule
{

    public ?int $reason;

    public function passes($attribute, $value)
    {
        if (!is_string($value) || !Str::startsWith($value, '+')) {
            return false;
        }
        try {
            $phoneUtil = \libphonenumber\PhoneNumberUtil::getInstance();
            $phone = $phoneUtil->parse($value);
            $this->reason = $phoneUtil->isPossibleNumberWithReason($phone);
            return $this->reason === \libphonenumber\ValidationResult::IS_POSSIBLE;
        } catch (\Exception $e) {
            return false;
        }
    }

    public function message()
    {
        return match ($this->reason) {
            \libphonenumber\ValidationResult::IS_POSSIBLE => 'The :attribute is not valid for an unknown reason.',
            \libphonenumber\ValidationResult::INVALID_COUNTRY_CODE => 'The :attribute does not have a valid country code.',
            \libphonenumber\ValidationResult::TOO_SHORT => 'The :attribute is too short.',
            \libphonenumber\ValidationResult::TOO_LONG => 'The :attribute is too long.',
            \libphonenumber\ValidationResult::IS_POSSIBLE_LOCAL_ONLY => 'The :attribute is not a valid phone number (local number).',
            \libphonenumber\ValidationResult::INVALID_LENGTH => 'The :attribute does not have a valid length.',
            default => 'The :attribute is not a valid phone number.',
        };
    }
}