PHP 整洁 'u'-标签被 'span' 取代

PHP Tidy 'u'-tag is replaced by 'span'

谁能帮忙找出 tidy 的问题?

下一行:

<p><u>Risk Warning</u><br />Please note that...</p>

之后:

$config = array(
            'clean' => true,
            'doctype' => '<!DOCTYPE HTML>',
            'drop-proprietary-attributes' => true,
            'output-xhtml' => true,
            'show-body-only' => true,
            'drop-font-tags' => false,
            'merge-spans' => true,
            'wrap' => '0',
            'ascii-chars' => false,
            'char-encoding' => 'utf8',
            'input-encoding' => 'utf8',
            'output-encoding' => 'utf8'
        );
$tidy = new \tidy();
$tidy->parseString($text, $config, 'utf8');
$tidy->cleanRepair();
echo tidy_get_output($tidy);

被替换为:

<p><span class="c1">Risk Warning</span><br />Please note that...</p>

如何防止 'u'-tag 更改?提前致谢。

$tidy->cleanRepair(); - 这里不需要