Contao\Input::stripTags PHP Method

    public static function stripTags($varValue, $strAllowedTags = '')
    {
        if ($varValue === null || $varValue == '') {
            return $varValue;
        }
        // Recursively clean arrays
        if (is_array($varValue)) {
            foreach ($varValue as $k => $v) {
                $varValue[$k] = static::stripTags($v, $strAllowedTags);
            }
            return $varValue;
        }
        // Encode opening arrow brackets (see #3998)
        $varValue = preg_replace_callback('@</?([^\\s<>/]*)@', function ($matches) use($strAllowedTags) {
            if ($matches[1] == '' || strpos(strtolower($strAllowedTags), '<' . strtolower($matches[1]) . '>') === false) {
                $matches[0] = str_replace('<', '&lt;', $matches[0]);
            }
            return $matches[0];
        }, $varValue);
        // Strip the tags and restore HTML comments
        $varValue = strip_tags($varValue, $strAllowedTags);
        $varValue = str_replace(array('&lt;!--', '&lt;!['), array('<!--', '<!['), $varValue);
        // Recheck for encoded null bytes
        while (strpos($varValue, '\\0') !== false) {
            $varValue = str_replace('\\0', '', $varValue);
        }
        return $varValue;
    }