respect-validation/library/Rules/PhpLabel.php

<?php

/*
 * This file is part of Respect/Validation.
 *
 * (c) Alexandre Gomes Gaigalas <alexandre@gaigalas.net>
 *
 * For the full copyright and license information, please view the LICENSE file
 * that was distributed with this source code.
 */

declare(strict_types=1);

namespace Respect\Validation\Rules;

use function is_string;
use function preg_match;

/**
 * Validates if a value is considered a valid PHP Label, so that it can be used as a variable, function or class name.
 *
 * @author Danilo Correa <danilosilva87@gmail.com>
 * @author Emmerson Siqueira <emmersonsiqueira@gmail.com>
 * @author Henrique Moody <henriquemoody@gmail.com>
 */
final class PhpLabel extends AbstractRule
{
    /**
     * {@inheritDoc}
     */
    public function validate($input): bool
    {
        return is_string($input) && preg_match('/^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$/', $input);
    }
}