php-parser/lib/PhpParser/Lexer/TokenEmulator/ReadonlyTokenEmulator.php

<?php declare(strict_types=1);

namespace PhpParser\Lexer\TokenEmulator;

use PhpParser\Lexer\Emulative;

final class ReadonlyTokenEmulator extends KeywordEmulator
{
    public function getPhpVersion(): string
    {
        return Emulative::PHP_8_1;
    }

    public function getKeywordString(): string
    {
        return 'readonly';
    }

    public function getKeywordToken(): int
    {
        return \T_READONLY;
    }
}